How do you know how long something takes?

For example:

The bus driver got to my house at 8:30 am. He had already been driving for 2 hours when he got to my house. When

did the bus driver start driving?

In this lesson, you will learn how to solve elapsed time

word problems in whole hour intervals by using a number

line.

Let’s ReviewMom put the cake in the oven at 4pm. The cake should cook for 45 minutes. When should she take it out of the oven?

4pm

45 minutes

?

Start time

End time

Change of time

Let’s Review

19 - 10 = 9

A Common Mistake

10:00am

11:00am

12:00pm

1:00pm

13:00pm

2:00pm

3:00pm

Forgetting that the hour after 12:00 is 1:00

Core Lesson

A baby takes a two hour nap in the

afternoon. If the baby goes to sleep at

1:10pm, what time will the baby wake

up? Start time

End time

Change of time

Core Lesson

Start time

1:10pm 2:10pm 3:10pm

End time

Core Lesson

The bus driver got to my house at 8:30

am. He had already been driving for 2

hours when he got to my house. When

did the bus driver start driving?

Start time

End time

Change of time

Core Lesson

Start time

6:30am 7:30am 8:30am

End time

In this lesson, you have learned how to solve elapsed time word problems in whole

hour intervals by using a number line.

Guided Practice

The movie began at 3:15 pm. The movie lasted 3 hours. What time did it end?

Extension Activities

Write your own elapsed time word problem and ask a partner to solve for the unknown part.

Extension Activities

Jeremy finished playing basketball at 6:30 pm. He played for 4 hours. What time did he start playing?

Extension Activities

The puppy fell asleep at 10:45 pm. He slept for 3 hours. What time did the puppy wake up?

Quick Quiz

1) The clock shows 12:45pm. What time will it be in 6 hours?

Quick Quiz

2) Alex goes to bed at 6:20pm. Tiffany goes to bed 3 hours later. What time does Tiffany go to bed?