Time

Units of Time

Choosing the Right Units of Time

Answer

Running 100 meters is a very quick event.
We need a small unit of time to measure it.
The best unit is seconds. Yay!
Answer: seconds.

Answer

Cleaning up a bedroom takes a short time, like 10 to 30 minutes.
We need a unit that’s not too small or too big to measure it.
The best unit is minutes.
Answer: minutes.

Answer

Your age is how many years you’ve lived, like 8 or 9 years.
We need a unit that measures a long time for people.
The best unit is years.
Answer: years.

Mcq

Which unit would you use to measure the time it takes to watch a movie?
Check one answer:

Seconds
Minutes
Hours
Days

Answer

Watching a movie takes a medium amount of time, like 1 to 2 hours.
We need a unit that’s not too small or too big to measure it.
The best unit is hours.
Answer: hours.

Mcq

Which unit would you use to measure the time it takes to go on a family camping trip?
Check one answer:

Seconds
Minutes
Hours
Days

Answer

A family camping trip usually takes a few days, like 3 to 5 days.
We need a unit that measures a few days, not too short or too long.
The best unit is days.
Answer: days.

Converting Units of Time

Converting Units of Time From Bigger to Smaller

Exercise

Convert 2 hours to minutes:2 h = min

Answer

$$\begin{aligned}2 \, \text{h} &= 2\times 60 \, \text{min} \\&= 120 \, \text{min}\end{aligned}$$

Exercise

Convert 3 days to hours:3 d = h

Answer

$$\begin{aligned}3 \, \text{d} &= 3 \times 24 \, \text{h} \\&= 72 \, \text{h}\end{aligned}$$

Exercise

Convert 5 minutes to seconds:5 min = s

Answer

$$\begin{aligned}5 \, \text{min} &= 5 \times 60 \, \text{s} \\&= 300 \, \text{s}\end{aligned}$$

Exercise

Convert 2 weeks to days:2 wk = d

Answer

$$\begin{aligned}2 \, \text{wk} &= 2 \times 7 \, \text{d} \\&= 14 \, \text{d}\end{aligned}$$

Converting Units of Time From Smaller to Bigger

Exercise

Convert 120 seconds to minutes:120 s = min

Answer

$$\begin{aligned}120 \, \text{s} &= 120 \div 60 \, \text{min} \\&= 2 \, \text{min}\end{aligned}$$

Exercise

Convert 24 hours to days:24 h = d

Answer

$$\begin{aligned}24 \, \text{h} &= 24 \div 24 \, \text{d} \\&= 1 \, \text{d}\end{aligned}$$

Exercise

Convert 180 minutes to hours:180 min = h

Answer

$$\begin{aligned}180 \, \text{min} &= 180 \div 60 \, \text{h} \\&= 3 \, \text{h}\end{aligned}$$

Exercise

Convert 14 days to weeks:14 d = wk

Answer

$$\begin{aligned}14 \, \text{d} &= 14 \div 7 \, \text{wk} \\&= 2 \, \text{wk}\end{aligned}$$

Dividing Time

Exercise

If you divide an hour into two equal parts, how many minutes are in half an hour?Half an hour = minutes

Answer

An hour has 60 minutes.
We divide it into two equal periods.
Splitting 60 by 2 gives: 60 $\div$ 2 = 30.
One half hour is 30 minutes.

Exercise

If you divide an hour into four equal parts, how many minutes are in one quarter of an hour?One quarter of an hour = minutes

Answer

An hour has 60 minutes.
We divide it into four equal periods.
Splitting 60 by 4 gives: 60 $\div$ 4 = 15.
One quarter hour is 15 minutes.

Exercise

If you divide a day into two equal parts, how many hours are in half a day?Half a day = hours

Answer

A day has 24 hours.
We divide it into two equal periods.
Splitting 24 by 2 gives: 24 $\div$ 2 = 12.
Half of a day is 12 hours.

Converting 1 Unit into 2 Units

Converting 2 Units into 1 Unit

Exercise

A movie lasts 1 hour 45 minutes. How many minutes is that?1 h 45 min = min

Answer

One hour is 60 minutes. Add the extra 45 minutes to find the total.
Calculate: $$ \begin{aligned} 1 \, \text{h} \, 45 \, \text{min} &= 1 \times 60 \, \text{min} + 45 \, \text{min} \\ &= 60 \, \text{min} + 45 \, \text{min} \\ &= 105 \, \text{min} \end{aligned} $$

Exercise

You hold your breath for 2 minutes 20 seconds. How many seconds is that?2 min 20 s = s

Answer

2 minutes is 120 seconds. Add the extra 20 seconds to find the total.
Calculate: $$ \begin{aligned} 2 \, \text{min} \, 20 \, \text{s} &= 2 \times 60 \, \text{s} + 20 \, \text{s} \\ &= 120 \, \text{s} + 20 \, \text{s} \\ &= 140 \, \text{s} \end{aligned} $$

Exercise

Your soccer practice lasts 1 hour 30 minutes. How many minutes is that?1 h 30 min = min

Answer

One hour is 60 minutes. Add the extra 30 minutes to find the total.
Calculate: $$ \begin{aligned} 1 \, \text{h} \, 30 \, \text{min} &= 1 \times 60 \, \text{min} + 30 \, \text{min} \\ &= 60 \, \text{min} + 30 \, \text{min} \\ &= 90 \, \text{min} \end{aligned} $$

Exercise

A trail running race lasts 1 day 5 hours. How many hours is that?1 d 5 h = h

Answer

One day is 24 hours. Add the extra 5 hours to find the total.
Calculate: $$ \begin{aligned} 1 \, \text{d} \, 5 \, \text{h} &= 1 \times 24 \, \text{h} + 5 \, \text{h} \\ &= 24 \, \text{h} + 5 \, \text{h} \\ &= 29 \, \text{h} \end{aligned} $$

Converting 1 Unit into 2 Units

Exercise

You read a book for 100 minutes. How many hours and minutes is that?100 min = h + min

Answer

One hour is 60 minutes. Divide 100 by 60 to find how many hours, and the rest is minutes.
Divide:
You get 1 hour, with 40 minutes left over, so: $$ \begin{aligned}[t] 100 \, \text{min} &= (1 \times 60 \, \text{min}) + 40 \, \text{min} \\ &= 1 \, \text{h} + 40 \, \text{min} \end{aligned} $$

Exercise

You run a race for 140 seconds. How many minutes and seconds is that?140 s = min + s

Answer

One minute is 60 seconds. Divide 140 by 60 to find how many minutes, and the rest is seconds.
Divide:
You get 2 minutes, with 20 seconds left over, so: $$ \begin{aligned}[t] 140 \, \text{s} &= (2 \times 60 \, \text{s}) + 20 \, \text{s} \\ &= 2 \, \text{min} + 20 \, \text{s} \end{aligned} $$

Exercise

You study for 150 minutes. How many hours and minutes is that?150 min = h + min

Answer

One hour is 60 minutes. Divide 150 by 60 to find how many hours, and the rest is minutes.
Divide:
You get 2 hours, with 30 minutes left over, so: $$ \begin{aligned}[t] 150 \, \text{min} &= (2 \times 60 \, \text{min}) + 30 \, \text{min} \\ &= 2 \, \text{h} + 30 \, \text{min} \end{aligned} $$

Exercise

You swim for 200 seconds. How many minutes and seconds is that?200 s = min + s

Answer

One minute is 60 seconds. Divide 200 by 60 to find how many minutes, and the rest is seconds.
Divide:
You get 3 minutes, with 20 seconds left over, so: $$ \begin{aligned}[t] 200 \, \text{s} &= (3 \times 60 \, \text{s}) + 20 \, \text{s} \\ &= 3 \, \text{min} + 20 \, \text{s} \end{aligned} $$

24-Hour Time Format

Telling Time the 24-Hour Way

Exercise

Your favorite show starts at 6:15 PM. What time is it in 24-hour time?:

Answer

Look at PM. Add 12 to the hours: 6 + 12 = 18.
Keep the minutes: 15 minutes.
Write the time: 18:15.

Exercise

You wake up at 7:45 AM for school. What time is it in 24-hour time?:

Answer

Look at AM. The hours stay the same: 7 hours.
Keep the minutes: 45 minutes.
Write the time: 07:45.

Exercise

Your soccer game starts at 4:30 PM. What time is it in 24-hour time?:

Answer

Look at PM. Add 12 to the hours: 4 + 12 = 16.
Keep the minutes: 30 minutes.
Write the time: 16:30.

Exercise

You eat dinner at 7:00 PM. What time is it in 24-hour time?:

Answer

Look at PM. Add 12 to the hours: 7 + 12 = 19.
Keep the minutes: 0 minutes.
Write the time: 19:00.

Finding Everyday Time from 24-Hour Clocks

Exercise

You have breakfast at 07:30. What time is it?:

Answer

Look at 07:30. It’s less than 12:00, so the hours stay 7.
Keep the minutes: 30 minutes.
Times before noon are AM.
Write the time: 7:30 AM.

Exercise

Your art class starts at 14:45. What time is it?:

Answer

Look at 14:45. It’s more than 12:00, so subtract 12 from the hours: 14 - 12 = 2.
Keep the minutes: 45 minutes.
Times after 12:00 are PM.
Write the time: 2:45 PM.

Exercise

You go to bed at 20:00. What time is it?:

Answer

Look at 20:00. It’s more than 12:00, so subtract 12 from the hours: 20 - 12 = 8.
Keep the minutes: 0 minutes.
Times after 12:00 are PM.
Write the time: 8:00 PM.

Exercise

Your music lesson starts at 15:20. What time is it?:

Answer

Look at 15:20. It’s more than 12:00, so subtract 12 from the hours: 15 - 12 = 3.
Keep the minutes: 20 minutes.
Times after 12:00 are PM.
Write the time: 3:20 PM.

Reading Clock Times

Reading Clocks

Exercise

You leave for school at the time shown on this clock. What time is it?

morning:

Answer

The little hand is past the 7 but not yet at the 8, so the hour is 7.
The big hand is between the 3 and 4. The 3 means $3\times 5=15$ minutes. Count 2 more marks after the 3: each mark is 1 minute, so 2 marks add 2 minutes.
Add: 15 minutes + 2 minutes = 17 minutes.
It’s morning, so the time is 7:17 AM.

Exercise

Your soccer practice starts at the time shown on this clock. What time is it?

afternoon:

Answer

The little hand is past the 4 but not yet at the 5, so the hour is 4.
The big hand is between the 7 and 8. The 7 means $7 \times 5 = 35$ minutes. Count 2 more marks after the 7: each mark is 1 minute, so 2 marks add 2 minutes.
Add: 35 minutes + 2 minutes = 37 minutes.
It’s afternoon, so the time is 4:37 PM.

Exercise

You eat breakfast at the time shown on this clock. What time is it?

morning:

Answer

The little hand is past the 8 but not yet at the 9, so the hour is 8.
The big hand is between the 4 and 5. The 4 means $4 \times 5 = 20$ minutes. Count 3 more marks after the 4: each mark is 1 minute, so 3 marks add 3 minutes.
Add: 20 minutes + 3 minutes = 23 minutes.
It’s morning, so the time is 8:23 AM.

Exercise

You watch a movie at the time shown on this clock. What time is it?

evening:

Answer

The little hand is past the 6 but not yet at the 7, so the hour is 6.
The big hand is between the 2 and 3. The 2 means $2 \times 5 = 10$ minutes. Count 4 more marks after the 2: each mark is 1 minute, so 4 marks add 4 minutes.
Add: 10 minutes + 4 minutes = 14 minutes.
It’s evening, so the time is 6:14 PM.

Reading Clocks for 24-Hour Time

Exercise

You leave for school at the time shown on this clock. What time is it in 24-hour format?

morning:

Answer

The little hand is past the 7 but not yet at the 8, so the hour is 7.
The big hand is between the 3 and 4. The 3 means $3 \times 5 = 15$ minutes. Count 2 more marks after the 3: each mark is 1 minute, so 2 marks add 2 minutes.
Add: 15 minutes + 2 minutes = 17 minutes.
It’s morning, so the hours stay the same. Add a zero before 7 for 24-hour time. The time is 07:17.

Exercise

Your soccer practice starts at the time shown on this clock. What time is it in 24-hour format?

afternoon:

Answer

The little hand is past the 4 but not yet at the 5, so the hour is 4.
The big hand is between the 7 and 8. The 7 means $7 \times 5 = 35$ minutes. Count 2 more marks after the 7: each mark is 1 minute, so 2 marks add 2 minutes.
Add: 35 minutes + 2 minutes = 37 minutes.
It’s afternoon, so add 12 to the hours: $4 + 12 = 16$. The time is 16:37.

Exercise

You eat breakfast at the time shown on this clock. What time is it in 24-hour format?

morning:

Answer

The little hand is past the 8 but not yet at the 9, so the hour is 8.
The big hand is between the 4 and 5. The 4 means $4 \times 5 = 20$ minutes. Count 3 more marks after the 4: each mark is 1 minute, so 3 marks add 3 minutes.
Add: 20 minutes + 3 minutes = 23 minutes.
It’s morning, so the hours stay the same. Add a zero before 8 for 24-hour time. The time is 08:23.

Exercise

You watch a movie at the time shown on this clock. What time is it in 24-hour format?

evening:

Answer

The little hand is past the 6 but not yet at the 7, so the hour is 6.
The big hand is between the 2 and 3. The 2 means $2 \times 5 = 10$ minutes. Count 4 more marks after the 2: each mark is 1 minute, so 4 marks add 4 minutes.
Add: 10 minutes + 4 minutes = 14 minutes.
It’s evening, so add 12 to the hours: $6 + 12 = 18$. The time is 18:14.

Add and Subtract Time

Adding Time

Exercise

You watch a movie for 1 hour 20 minutes and do homework for 1 hour 15 minutes. How long is that altogether? h min

Answer

Add the minutes: 20 minutes + 15 minutes = 35 minutes.
Since 35 minutes is less than 60, no extra hour is needed.
Add the hours: 1 hour + 1 hour = 2 hours.
So, you spent 2 hours and 35 minutes altogether.
$$ \begin{aligned}[t] 1 \, \text{h} \, 20 \, \text{min} + 1 \, \text{h} \, 15 \, \text{min} &= (1 \, \text{h} + 1 \, \text{h}) + (20 \, \text{min} + 15 \, \text{min}) \\ &= 2 \, \text{h} + 35 \, \text{min} \\ &= 2 \, \text{h} \, 35 \, \text{min} \end{aligned} $$

Exercise

You ride your bike for 1 hour 25 minutes and play soccer for 1 hour 30 minutes. How long is that altogether? h min

Answer

Add the minutes: 25 minutes + 30 minutes = 55 minutes.
Since 55 minutes is less than 60, no extra hour is needed.
Add the hours: 1 hour + 1 hour = 2 hours.
So, you spent 2 hours and 55 minutes altogether.
$$ \begin{aligned}[t] 1 \, \text{h} \, 25 \, \text{min} + 1 \, \text{h} \, 30 \, \text{min} &= (1 \, \text{h} + 1 \, \text{h}) + (25 \, \text{min} + 30 \, \text{min}) \\ &= 2 \, \text{h} + 55 \, \text{min} \\ &= 2 \, \text{h} \, 55 \, \text{min} \end{aligned} $$

Exercise

You spend 1 hour 15 minutes on Math homework and 55 minutes on Science homework. How long is that altogether? h min

Answer

Add the minutes: 15 minutes + 55 minutes = 70 minutes.
Too many minutes! 70 minutes is more than 60, so take 60 minutes (1 hour) and keep 10 minutes: 70 min = 1 h 10 min.
Add the hours: 1 hour + 0 hours + 1 hour (extra hour) = 2 hours.
So, you spent 2 hours and 10 minutes altogether.
$$ \begin{aligned}[t] 1 \, \text{h} \, 15 \, \text{min} + 55 \, \text{min} &= 1 \, \text{h} + (15 \, \text{min} + 55 \, \text{min}) \\ &= 1 \, \text{h} + 70 \, \text{min} \\ &= 1 \, \text{h} + (1 \, \text{h} + 10 \, \text{min}) \\ &= 2 \, \text{h} \, 10 \, \text{min} \end{aligned} $$

Exercise

You play a game for 2 hours 30 minutes and read a book for 1 hour 45 minutes. How long is that altogether? h min

Answer

Add the minutes: 30 minutes + 45 minutes = 75 minutes.
Too many minutes! 75 minutes is more than 60, so take 60 minutes (1 hour) and keep 15 minutes: 75 min = 1 h 15 min.
Add the hours: 2 hours + 1 hour + 1 hour (extra hour) = 4 hours.
So, you spent 4 hours and 15 minutes altogether.
$$ \begin{aligned}[t] 2 \, \text{h} \, 30 \, \text{min} + 1 \, \text{h} \, 45 \, \text{min} &= (2 \, \text{h} + 1 \, \text{h}) + (30 \, \text{min} + 45 \, \text{min}) \\ &= (2 \, \text{h} + 1 \, \text{h}) + 75 \, \text{min} \\ &= (2 \, \text{h} + 1 \, \text{h}) + (1 \, \text{h} + 15 \, \text{min}) \\ &= 4 \, \text{h} \, 15 \, \text{min} \end{aligned} $$

Subtracting Time

Exercise

You have 3 hours 40 minutes to finish your chores. You spend 1 hour 25 minutes cleaning your room. How much time is left? h min

Answer

Subtract the minutes: 40 minutes - 25 minutes = 15 minutes.
Enough minutes, so no borrowing is needed.
Subtract the hours: 3 hours - 1 hour = 2 hours.
So, you have 2 hours and 15 minutes left.
$$ \begin{aligned}[t] 3 \, \text{h} \, 40 \, \text{min} - 1 \, \text{h} \, 25 \, \text{min} &= (3 \, \text{h} - 1 \, \text{h}) + (40 \, \text{min} - 25 \, \text{min}) \\ &= 2 \, \text{h} + 15 \, \text{min} \\ &= 2 \, \text{h} \, 15 \, \text{min} \end{aligned} $$

Exercise

You have 2 hours 35 minutes before dinner. You spend 1 hour 20 minutes practicing piano. How much time is left? h min

Answer

Subtract the minutes: 35 minutes - 20 minutes = 15 minutes.
Enough minutes, so no borrowing is needed.
Subtract the hours: 2 hours - 1 hour = 1 hour.
So, you have 1 hour and 15 minutes left.
$$ \begin{aligned}[t] 2 \, \text{h} \, 35 \, \text{min} - 1 \, \text{h} \, 20 \, \text{min} &= (2 \, \text{h} - 1 \, \text{h}) + (35 \, \text{min} - 20 \, \text{min}) \\ &= 1 \, \text{h} + 15 \, \text{min} \\ &= 1 \, \text{h} \, 15 \, \text{min} \end{aligned} $$

Exercise

You have 4 hours 10 minutes to complete your tasks. You spend 2 hours 45 minutes organizing your books. How much time is left? h min

Answer

Subtract the minutes: 10 minutes - 45 minutes. Not enough minutes! Borrow 1 hour (60 minutes) from the 4 hours, leaving 3 hours. Add 60 minutes to 10 minutes: 10 + 60 = 70 minutes.
Now subtract: 70 minutes - 45 minutes = 25 minutes.
Subtract the hours: 3 hours - 2 hours = 1 hour.
So, you have 1 hour and 25 minutes left.
$$ \begin{aligned}[t] 4 \, \text{h} \, 10 \, \text{min} - 2 \, \text{h} \, 45 \, \text{min} &= 3 \, \text{h} \, 70 \, \text{min} - 2 \, \text{h} \, 45 \, \text{min} \\ &= (3 \, \text{h} - 2 \, \text{h}) + (70 \, \text{min} - 45 \, \text{min}) \\ &= 1 \, \text{h} \, 25 \, \text{min} \end{aligned} $$

Exercise

You have 3 hours 15 minutes to work on a project. You spend 1 hour 40 minutes writing a story. How much time is left? h min

Answer

Subtract the minutes: 15 minutes - 40 minutes. Not enough minutes! Borrow 1 hour (60 minutes) from the 3 hours, leaving 2 hours. Add 60 minutes to 15 minutes: 15 + 60 = 75 minutes.
Now subtract: 75 minutes - 40 minutes = 35 minutes.
Subtract the hours: 2 hours - 1 hour = 1 hour.
So, you have 1 hour and 35 minutes left.
$$ \begin{aligned}[t] 3 \, \text{h} \, 15 \, \text{min} - 1 \, \text{h} \, 40 \, \text{min} &= 2 \, \text{h} \, 75 \, \text{min} - 1 \, \text{h} \, 40 \, \text{min} \\ &= (2 \, \text{h} - 1 \, \text{h}) + (75 \, \text{min} - 40 \, \text{min}) \\ &= 1 \, \text{h} \, 35 \, \text{min} \end{aligned} $$

Exercise

You have 4 hours 15 minutes of free time. You play a game for 1 hour 45 minutes. How much time is left? h min

Answer

Subtract the minutes: 15 minutes - 45 minutes. Not enough minutes! Borrow 1 hour (60 minutes) from the 4 hours, leaving 3 hours. Add 60 minutes to 15 minutes: 15 + 60 = 75 minutes.
Now subtract: 75 minutes - 45 minutes = 30 minutes.
Subtract the hours: 3 hours - 1 hour = 2 hours.
So, you have 2 hours and 30 minutes left.
$$ \begin{aligned}[t] 4 \, \text{h} \, 15 \, \text{min} - 1 \, \text{h} \, 45 \, \text{min} &= 3 \, \text{h} 75 \, \text{min} - 1 \, \text{h}\,20 \, \text{min} \\ &= (3 \, \text{h} - 1 \, \text{h}) + (75 \, \text{min} - 45 \, \text{min}) \\ &= 2 \, \text{h} \, 30 \, \text{min} \\ \end{aligned} $$

Time Problems

Figuring Out Time

Exercise

You work 2 hours 30 minutes on Saturday and 1 hour 20 minutes on Sunday. How much time do you work altogether? h min

Answer

Add the minutes: 30 minutes + 20 minutes = 50 minutes.
Add the hours: 2 hours + 1 hour = 3 hours.
So, you work 3 hours and 50 minutes altogether.
$$ \begin{aligned}[t] 2 \, \text{h} \, 30 \, \text{min} + 1 \, \text{h} \, 20 \, \text{min} &= (2 \, \text{h} + 1 \, \text{h}) + (30 \, \text{min} + 20 \, \text{min}) \\ &= 3 \, \text{h} + 50 \, \text{min} \\ &= 3 \, \text{h} \, 50 \, \text{min} \end{aligned} $$

Exercise

A train starts at 8:20 AM and arrives at 1:30 PM. How long is the train journey? h min

Answer

Subtract the minutes: 30 minutes - 20 minutes = 10 minutes.
Subtract the hours: 13 hours - 8 hours = 5 hours.
So, the train journey takes 5 hours and 10 minutes.
$$ \begin{aligned}[t] 13 \, \text{h} \, 30 \, \text{min} - 8 \, \text{h} \, 20 \, \text{min} &= (13 \, \text{h} - 8 \, \text{h}) + (30 \, \text{min} - 20 \, \text{min}) \\ &= 5 \, \text{h} + 10 \, \text{min} \\ &= 5 \, \text{h} \, 10 \, \text{min} \end{aligned} $$

Exercise

Liam has to wrap 12 gift boxes for a charity event. It takes him 3 minutes to wrap each box. How long will it take to wrap all the gift boxes? min

Answer

Find the total time: 12 gift boxes, and each takes 3 minutes.
Multiply: $12 \times 3 = 36$ minutes.
So, Liam will need 36 minutes to wrap all the gift boxes.
$$ \begin{aligned}[t] 12 \times 3 \, \text{min} &= 36 \, \text{min} \end{aligned} $$

Exercise

A teacher has 36 minutes to grade tests. Each test takes 3 minutes to grade. How many tests can the teacher grade? tests

Answer

Find the number of tests: 36 minutes, and each test takes 3 minutes.
Divide: 36 minutes ÷ 3 minutes per test = 12 tests.
So, the teacher can grade 12 tests.
$$ \begin{aligned}[t] 36 \, \text{min} \div 3 \, \text{min per test} &= 12 \end{aligned} $$

Exercise

You spend 1 hour 40 minutes mixing cookie dough and 1 hour 25 minutes decorating the cookies. How long do you spend baking altogether? h min

Answer

Add the minutes: 40 minutes + 25 minutes = 65 minutes.
Too many minutes! 65 minutes is more than 60, so take 60 minutes (1 hour) and keep 5 minutes: 65 min = 1 h 5 min.
Add the hours: 1 hour + 1 hour + 1 hour (extra hour) = 3 hours.
So, you spend 3 hours and 5 minutes baking altogether.
$$ \begin{aligned}[t] 1 \, \text{h} \, 40 \, \text{min} + 1 \, \text{h} \, 25 \, \text{min} &= (1 \, \text{h} + 1 \, \text{h}) + (40 \, \text{min} + 25 \, \text{min}) \\ &= (1 \, \text{h} + 1 \, \text{h}) + 65 \, \text{min} \\ &= (1 \, \text{h} + 1 \, \text{h}) + (1 \, \text{h} + 5 \, \text{min}) \\ &= 3 \, \text{h} \, 5 \, \text{min} \end{aligned} $$

Exercise

Sofia needs to bake 15 cupcakes for a school event. Each cupcake takes 5 minutes to prepare. How long will it take to bake all the cupcakes? h min

Answer

Find the total time: 15 cupcakes, and each takes 5 minutes.
Multiply: $15 \times 5 = 75$ minutes.
Convert: 75 minutes = 60 minutes + 15 minutes = 1 h 15 min.
So, Sofia will need 1 hour and 15 minutes to bake all the cupcakes.
$$ \begin{aligned}[t] 15 \times 5 \, \text{min} &= 75 \, \text{min} \\ &= 60 \, \text{min} + 15 \, \text{min} \\ &= 1 \, \text{h} \, 15 \, \text{min} \end{aligned} $$

Exercise

To plant the vegetables, it takes me 20 hours, and I work over 4 days. How many hours do I work per day? hours per day

Answer

Find the hours per day: 20 hours total, spread over 4 days.
Divide: 20 hours ÷ 4 days = 5 hours per day.
So, I work 5 hours per day.
$$ \begin{aligned}[t] 20 \, \text{hours} \div 4 \, \text{days} &= 5 \, \text{hours per day} \end{aligned} $$

Exercise

In a library, I begin to work at 8:30 AM, and I finish at 10:20 AM. How much time do I work? h min

Answer

Subtract the minutes: 20 minutes - 30 minutes. Not enough minutes! Borrow 1 hour (60 minutes) from the 10 hours, leaving 9 hours. Add 60 minutes to 20 minutes: 20 + 60 = 80 minutes.
Now subtract: 80 minutes - 30 minutes = 50 minutes.
Subtract the hours: 9 hours - 8 hours = 1 hour.
So, I work for 1 hour and 50 minutes.
$$ \begin{aligned}[t] 10 \, \text{h} \, 20 \, \text{min} - 8 \, \text{h} \, 30 \, \text{min} &= 9 \, \text{h} \, 80 \, \text{min} - 8 \, \text{h} \, 30 \, \text{min} \\ &= (9 \, \text{h} - 8 \, \text{h}) + (80 \, \text{min} - 30 \, \text{min}) \\ &= 1 \, \text{h} \, 50 \, \text{min} \end{aligned} $$