All the solutions provided inÂ **McGraw Hill My Math Grade 4 Answer Key PDF Chapter 12 Lesson 1 Metric Units of Length **will give you a clear idea of the concepts.

## McGraw-Hill My Math Grade 4 Answer Key Chapter 12 Lesson 1 Metric Units of Length

Length is the measurement of a line between two points. Millimeter, centimeter, meter, and kilometer are units that are part of the metric system of measure for length.

**Math in My World**

**Example 1**

Doug is growing carrots in his garden. He pulled out a carrot for lunch. Measure the carrot to the nearest centimeter.

The carrot is closer to the 12â€”centimeter mark than the 11-centimeter mark.

So, the carrot is almost ________________ centimeters long.

Answer: So, the carrot is almost 12 centimeters long.

Explanation: Given that,

Doug is growing carrots in his garden.

He pulled out a carrot for lunch.

Now, we will find the carrot nearest centimeter.

So, based on the given image the carrot is closer to the 12centimeter mark than the 11cm mark.

i.,e 12 x 10 = 120mm

120 millimeters is equal to 12cm.

Therefore, the carrot is almost 12 centimeters long.

**Example 2**

Choose the best estimate for the length of a student’s desk.

10 millimeters = 1 centimeter

(A) 5 centimeters

(B) 5 millimeters

(C) 50 centimeters

(D) 50 millimeters

A desk has to be long enough to work on. So, centimeters are a better estimate than millimeters.

Since 5 centimeters, 5 millimeters, and 50 millimeters are all too small, the answer is _______________, or choice ______________.

Answer: Since 5 centimeters, 5 millimeters, and 50 millimeters are all too small, the answer is 50 cm or choice C.

Explanation: Given the figure.

The figure consists of a rectangular table.

The table is in rectangle form.

Now, we will find the length of the table.

Consider that 1m = 100 cm

1/2 m = 50 cm

Since 5 centimeters, 5 millimeters, and 50 millimeters are too small. The best estimation for length is 50 cm.

**Guided Practice**

Question 1.

Estimate the length of the grasshopper. Then measure to the nearest centimeter.

Answer: 3cm

Explanation: Given the figure.

Now, we will find the length of the grasshopper to the nearest centimeter.

Using the scale we can measure easily.

Place the 0 points on the scale at the starting line and measure it.

So, it will be 3 x 10 mm = 30 mm

30 mm = 3cm.

Hence, the length of the grasshopper is 3cm.

Question 2.

Choose the best estimate for the length of the kayak.

(A) 6 centimeters

(B) 2 meters

(C) 6 meters

(D) 2 kilometers

Answer: Option B

Explanation: Given the figure.

Now, we will find the length of the kayak.

The best estimate is 2 meters.

Because in the given option 6 cm is too small.

The 6 meters is very long and 2km is not suited because the unit given is wrong.

So, it will be 2m.

200 cm = 2m.

Hence, the length of the kayak is 2m.

**Talk Math**

Describe a situation when it would be appropriate to measure an object using millimeters.

Answer: While describing various physical quantities, it is best to use appropriate units of measure. Using other units of measure to describe a quantity gives either a very small or very large number value. It becomes difficult to estimate the magnitude of the quantity if in appropriate units millimeters are used.

**Independent Practice**

**Estimate each length. Then measure each object to the nearest centimeter.**

Question 3.

Length: ______________

Answer: The length is 6 cm.

Explanation: Given the figure.

Now, we will find the length of the given figure to the nearest centimeter.

Using the scale we can measure easily.

Place the 0 points on the scale at the starting line and measure it.

So, it will be 6 x 10 mm = 60 mm

i.e., 60 mm = 6 cm.

Hence, the length of the crab is 6 cm.

Question 4.

Length: ______________

Answer: The length is 2 cm.

Explanation: Given the figure.

Now, we will find the length of the button to the nearest centimeter.

Using the scale we can measure easily.

Place the 0 points on the scale at the starting line and measure it.

So, it will be 2 x 10 mm = 20 mm

i..e, 20 mm = 2 cm.

Hence, the length of the button is 2 cm.

Question 5.

Length: ______________

Answer: The length of the watch is 4 cm.

Explanation: Given the figure.

Now, we will find the length of the watch to the nearest centimeter.

Using the scale we can measure easily.

Place the 0 points on the scale at the starting line and measure it.

So, it will be 4 x 10 mm = 40 mm

i.e., 40 mm = 4cm.

Hence, the length of the watch is 4cm.

Question 6.

Length: ______________

Answer: 6 cm

Explanation: Given the figure.

Now, we will find the length of the Eraser to the nearest centimeter.

Using the scale we can measure easily.

Place the 0 points on the scale at the starting line and measure it.

So, it will be 6 x 10 mm = 60 mm.

Then it is 60 mm = 6 cm.

Therefore, the length of the Eraser is 6 cm.

**Choose the best estimate for each length.**

Question 7.

height of a cornstalk

(A) 2 millimeters

(B) 2 centimeters

(C) 2 meters

(D) 2 kilometers

Answer: Option C

Explanation: Given the figure.

Now, we will find the height of the cornstalk.

So, it will be 2 meters.

Hence, the Height of the cornstalk is 2 meters.

Question 8.

length of an airport runway

(A) 5 millimeters

(B) 50 centimeters

(C) 5 meters

(D) 5 kilometers

Answer: Option D

Explanation: Given the figure.

Now, we will find the length of an airport runway to the nearest kilometers.

So, it will be 5 x 1000 m = 5000 m.

5000 m = 5km.

Hence, the length of an airport runway is 5km.

**Problem Solving**

Question 9.

A giraffe at the zoo is 5 meters tall. Name something else that is about 5 meters tall.

Answer: The tree is about 5 meters tall.

Question 10.

Is the distance from Boston, Massachusetts, to Phoenix, Arizona, about 4,000 centimeters or 4,000 kilometers? Explain.

Answer: The distance from Boston to phoenix is too long. So, 4000 km is reasonable.

Question 11.

**Mathematical PRACTICE** Justify Conclusions Why would it be better to measure the length of your classroom with a meterstick instead of a centimeter ruler?

Answer: A meterstick is longer than a centimeter ruler. Since a classroom’s length is many meters long, a meterstick would be the better measurement tool to use.

**HOT Problems**

Question 12.

**Mathematical PRACTICE** Use Math Tools Find three things in the classroom that are longer than 10 centimeters and smaller than 100 centimeters.

Answer: The three things in the classroom that are longer than 10 cm and smaller than 100 cm is a pencil, a keyboard, and a sheet of A4 paper.

Question 13.

**Building on the Essential Question** Is it reasonable to use centimeters to measure the length of any object? Explain.

Answer: No, it’s reasonable to use centimeters to measure the length of any object. Centimeters should be used to measure small objects but not large objects because it would be too difficult to measure the length of large objects in centimeters.

### McGraw Hill My Math Grade 4 Chapter 12 Lesson 1 My Homework Answer Key

**Practice**

**Estimate each length. Then measure each object to the nearest centimeter.**

Question 1.

Length: ________________

Answer: The length of the clarinet is 7cm.

Explanation: Given the figure.

Now, we will find the length of the clarinet to the nearest centimeter.

Using the scale we can measure easily.

Place the 0 points on the scale at the starting line and measure it.

So, it will be 7 x 10 mm = 70 mm

70 mm = 7cm.

Hence, the length of the clarinet is 7cm.

Question 2.

Length: ________________

Answer: The length is 2 cm.

Explanation: Given the figure.

Now, we will find the length of the figure to the nearest centimeter.

Using the scale we can measure easily.

Place the 0 points on the scale at the starting line and measure it.

So, it will be 2 x 10 mm = 20 mm.

20 mm = 2cm.

Hence, the length of the figure is 2cm.

Question 3.

Length: ________________

Answer: The length of the Hoagie Roll is 3cm.

Explanation: Given the figure.

Now, we will find the length of the Hoagie Roll.

Using the scale we can measure easily.

Place the 0 points on the scale at the starting line and measure it.

So, it will be 4 x 10 mm = 40 mm.

40 mm = 4cm.

Hence, the length of the Hoagie Roll is 4cm.

**Choose the best estimate for each length.**

Question 4.

length of a river

(A) 27 km

(B) 7 m

(C) 170 cm

(D) 270 mm

Answer: Option A

Explanation: Given that,

Now, we will find the length of a river.

Generally, the rivers are measured in km and miles.

Based on the given option, the estimated length is option A it is in kilometers.

Hence, the estimated length of a river is 27km.

Question 5.

length of a sunflower seed

(A) 90 cm

(B) 90 mm

(C) 9 cm

(D) 9 mm

Answer: Option D

Explanation: Given that,

Now, we will find the length of a sunflower seed.

The length of a sunflower seed is 7mm to 9mm.

Based on the given option, the length is 9 x 1mm = 9 mm.

Hence, the estimated length of the sunflower seed is 9mm.

**Problem Solving**

Question 6.

**Mathematical PRACTICE** Draw a Conclusion Sonia is standing 20 centimeters from the door. Brice is standing 20 meters from the door. Who is standing farther from the door?

Answer: Brice is standing farther from the door.

Explanation: Given that,

Sonia is standing 20 centimeters from the door.

Brice is standing 20 meters from the door.

Now, we will find the person who is farther from the door.

The Brice is farther from the door. Because meters are bigger than centimeters. To change meters to centimeters you would have to multiply by 10 or 100 to get it.

So, the brice is farther from the door.

Question 7.

Carly says she walks 300 millimeters to school each day. Is this reasonable? Explain.

Answer: No, as 300 millimeters is only 30 centimeters, which in turn is only 11.811 inches. It is very improbable that she would only need to walk 11.811 inches to school each day.

Question 8.

At his auntâ€™s farm, Benjamin sees a horse that is 2 meters long. Name two other things that are about 2 meters long.

Answer: Benjamin sees a horse that is 2 meters long. The two other things that are about 2 meters long are, two meters is equal to about 6 and a half feet. So, the other two things are trees and doors.

**Vocabulary Check**

Question 9.

List the metric system units for measuring length in order from greatest to least.

centimeter

kilometer

meter

millimeter

Answer: The metric system units for measuring length in order from greatest to least a kilometer, meter, centimeter, and millimeter.

**Test Practice**

Question 10.

Which is the best unit to use for measuring the length of an eyelash?

(A) millimeter

(B) centimeter

(C) meter

(D) kilometer

Answer: Option A

Explanation: Given that,

Now, we will find the best unit to measure the length of an eyelash.

The best unit to use for measuring the length of an eyelash is millimeters. Because there are small in size.

So, the units of millimeters are enough for that to measure.

Hence, the unit for the length of an eyelash is millimeters.