We included **HMH Into Math Grade 4 Answer Key PDF** **Module 21 Lesson 1 Compare Units of Time **to make students experts in learning maths.

## HMH Into Math Grade 4 Module 21 Lesson 1 Answer Key Compare Units of Time

I Can represent and compare units of time given in hours, minutes, and seconds.

**Spark Your Learning**

A train engineer uses the station clock and a wristwatch to record the times that trains depart and arrive. These clocks show the time that the A train left one morning. What time does each clock show?

Answer:

The time shown on the station clock and wrist clock is **11:02**.

Explanation:

A train engineer uses both the station clock and a wristwatch to record the times that trains depart and arrive. The above two clocks show the time that the A train left on morning. The hours hand is at 11. The minute hand is is in between 12 and 1. So, both the station clock and wrist clock shows the time as 11:02.

**Turn and Talk** What do you think the small, red hand on the engineer’s wristwatch represents?

Answer:

The red hand on the engineer’s wristwatch represents **seconds hand**.

**Build Understanding**

Question 1.

Marlis and Jacoby compete in a half marathon. They started the race at noon. The clock shows the time they finished the race in the afternoon.

A. Write the time that Marlis and Jacoby finished the race.

Answer:

Marlis and Jacoby finished the race at 2:27 P.M.

B. Marlis crossed the finish line ahead of Jacoby. How is this possible?

Answer:

C. The runners’ exact finishing times are shown on the clock faces. Write the exact times that Marlis and Jacoby finished the race.

Marlis: ___________

Jacoby:___________

Answer:

The runners’ exact finishing times are shown on the above two clock faces. The exact time that Marlis finished the race in 02: 26: 39. The exact time that Jacoby finished the race in 02: 27: 07.

**Turn and Talk** How does the length of a second compare with the length of an hour?

Answer:

One second is equal to **1/3,600** of one hour.

**Step It Out**

Question 2.

Alden spent 4 hours on his science project. Natasha spent 250 minutes on her science project. Who spent more time on the science project, Alden or Natasha?

A. Complete the table.

Answer:

B. How many minutes did Alden spend on his science project?

Answer:

Alden spent **240 minutes** on his science project.

Explanation:

Alden spent 4 hours on his science project.

1 hour is equal to 60 minutes. To convert hours into minutes we need to perform multiplication operation.

Multiply 4 with 60 the product is equal to 240 minutes.

4 x 60 = 240 minutes

So, Alden spent **240 minutes** on his science project.

C. Compare Alden and Natasha’s times.

4 hours 250 minutes

Answer:

4 hours 250 minutes

4 hours is equal to 240 minutes. So, 240 minutes is less than 250 minutes.

D. Who spent more time on the science project?

Answer:

**Natasha** spent more time on the science project.

**Check Understanding**

Question 1.

Lian spent 3 minutes doing jumping jacks. Ruiz spent 175 seconds doing jumping jacks. Who spent a greater amount of time doing jumping jacks? Use the table to solve.

_________ spent a greater amount of time doing jumping jacks.

Answer:

Lian spent a greater amount of time doing jumping jacks.

Explanation:

Lian spent 3 minutes doing jumping jacks. Ruiz spent 175 seconds doing jumping jacks. We know that 1 minute is equal to 60 seconds. To convert 3 minutes into seconds we need to perform multiplication operation. Multiply 60 with 3 the product is equal to 180 seconds. Lian spent 180 seconds doing jumping jacks. So, Lian spent a greater amount of time doing jumping jacks.

Question 2.

Write the time shown on the clock.

Answer:

The time is **4:30**.

Explanation:

The hours hand is in between 4 and 5. The minute hand is at 6 which implies 30 minutes(6 x 5). So, the time shown on the above clock is 4:30.

Question 3.

Which represents a greater amount of time? Circle your answer.

2 hours

100 minutes

Answer:

Explanation:

We know that 1 hour is equal to 60 minutes. The given times are 2 hours and 100 minutes. Two hours is equal to 120 minutes(60 x 2). The greater amount of time is represented by 2 hours compared to 100 minutes. So, draw a circle for 2 hours.

**On Your Own**

Question 4.

**Use Structure** Dora says that there are 7,200 seconds in 2 hours. Hector says that there are 6,000 seconds in 2 hours. Is either statement correct? Use tables to support your explanation.

Answer:

Explanation:

We know that 1 hour is equal to 60 minutes and 1 minute is equal to 60 seconds.

To convert 2 hours in seconds we need to perform multiplication operation.

Multiply 120 with 60 the product is equal to 7,200.

120 x 60 = **7,200 seconds**

There are 7,200 seconds in 2 hours. So, Dora statement is correct.

Question 5.

**Reason** Last week, Ricardo spent 160 minutes practicing the piano. Taci spent 2\(\frac{1}{2}\) hours practicing the piano. Who spent more time practicing, Ricardo or Taci? Explain.

Answer:

Ricardo spent **160 minutes** for practicing the piano.

Taci spent 2\(\frac{1}{2}\) hours for practicing the piano.

Convert the mixed fraction hours to fraction hours.

2\(\frac{1}{2}\) hours

Multiply the denominator value 2 with the numerator value 2 then add the product to the 1.

= [(2 x 2) + 1]/2 hours

= 5/2 hours

= **2.5 hours**

We know that 1 hour is equal to 60 minutes. Convert 2.5 hours into minutes.

1 hour = 60 minutes

2.5 hours = ? minutes

Multiply 2.5 with 60 the product is equal to 150 minutes.

So, 2.5 hours is equal to **150 minutes.
**Taci spent 150 minutes for practicing the piano.

**Ricardo**spent more time for practicing the piano.

**Complete.**

Question 6.

3 hours = ________ minutes

Answer:

We know that 1 minutes is equal to 60 seconds and 1 hour is equal to 60 minutes.

1 hour = 60 minutes

3 hours = ? minutes

Multiply 3 with 60 the product is equal to 180 minutes.

So, three hours is equal to **180 minutes**.

Question 7.

5 minutes = _________ seconds

Answer:

We know that 1 minutes is equal to 60 seconds.

1 minute = 60 seconds

5 minutes = ? seconds

Multiply 5 with 60 the product is equal to 300 seconds.

So, five minutes is equal to** 300 seconds**.

**Write whether you would use hours, minutes, or seconds to measure how long it takes to complete the activity.**

Question 8.

walk to school _________

Answer:

walk to school : **Minutes**

Explanation:

Usually the school will be in a walkable distance. The distance is not too short to measure in seconds and its not too long to measure in hours. So, the appropriate word would be minutes.

Question 9.

throw a ball 20 feet __________

Answer:

throw a ball 20 feet : **seconds**

Explanation:

The action of throwing a ball will be done in seconds. So, the appropriate word would be seconds.

**I’m in a Learning Mindset!**

How did I learn from the way my classmates solved problems comparing units of time?