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Time Word Problem

In word problems that involve time, you need to think and analyse the problem carefully.

Few tips to help you solve word problems that involve time:

1. Remember that the time is based on 12, not 10. So, we can’t always add or subtract the hour and minutes. Therefore, we count the time.

For example: What would be the time 3 hours after 11:00 AM?

We know that 1 hour later will be 12:00 noon, 2 hours later will be 1:00 PM and 3 hours later will be 2:00 PM. Hence, 3 hours after 11: 00 AM will be 2:00 PM.

2. Remember to include AM/PM.

3. After solving the question, always ask yourself if your answer makes sense.

Let's take a look at some examples:

1. Alfred goes to school at 8:15 AM and comes back home at 3:00 PM. How much time is passed?

Let’s count the time to solve this problem.

Total minutes from 8:15 AM to 9:00 AM = 45 minutes (1 hour = 60 minutes, so 60 – 15 = 45 minutes).

Now, let’s count the hours from 9:00 AM to 3:00 PM

9 - 12 makes 3 hours

12 - 3 makes 3 hours

So, 9 -3 makes 6 hours

6 hours plus 45 minutes

Answer: 6 hours, 45 minutes.

Is this a reasonable amount of time for him to be at school?

Yes it is.

2. It is 7:50 PM and Lydia needs to practice the piano for 30 minutes. What time will it be when she finish her practice?

We need to add 30 minutes to 7:50, but we can’t just add the minutes because we’d get 7:80 and there is no such time.

Total minutes from 7:50 PM to 8:00 PM = 10 minutes (there are 60 minutes in an hour, 60 – 50 = 10)

How much time she will be left with?

30 minutes – 10 minutes = 20 minutes.

She’ll still have 20 minutes left.

What is 20 minutes after 8:00?

It is 8:20.

Answer: 8:20 PM

Does this answer make sense?

Yes, if she starts at 7:50 PM and practices for 30 minutes, it makes sense that she’d finish her practice at 8:20 PM.

3. Anton and Titus mowed lawns for 3 hours and 20 minutes. They finished at 1:30 PM. What time did they start?

In this, we need to work backwards to figure out what time they started.

Let’s start by working with the minutes:

What time is 20 minutes before 1:30 PM?  

30 – 20 = 10

So, it is 1:10 PM

Now we need to know what is 3 hours before 1:10 PM?

Let’s count backwards:

1 hour before would be 12:10 PM.

2 hours before would be 11:10 AM (We changed it to AM, since the time is before noon).

3 hours before would be 10:10 AM.

Answer: 10:10 AM

Does this answer make sense?

Yes, 10:10 AM plus 3 hours and 20 minutes would be 1:30 PM.

Summary

1. Remember that the time is based on 12, not 10. So, we can’t always add or subtract the hour and minutes. Therefore, we count the time.

For example: What would be the time 3 hours after 11:00 AM?

We know that 1 hour later will be 12:00 noon, 2 hours later will be 1:00 PM, and 3 hours later will be 2:00 PM. Hence, 3 hours after 11: 00 AM will be 2:00 PM.

2. Remember to include AM/PM.

3. After solving the question, always ask yourself if your answer makes sense.

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