## Envision Math 3rd Grade Textbook Answer Key Topic 2.2 Rounding 2- and 3-Digit Numbers

**Rounding 2- and 3-Digit Numbers**

How can you round numbers?

To the nearest 10, about how many rocks does Tito have?

Answer:

Round 394 to the nearest ten. To round, replace a number with a number that tells about how many.

**Another Example**

How can you round to the nearest hundred?

Answer:

To the nearest hundred, about how many rocks does Donna have?

Round 350 to the nearest hundred.

**One Way**

You can use a number line.

If a number is halfway between, round to the greater number.

350 is halfway between 300 and 400, so 350 rounds to 400.

**Another Way**

You can use place value.

Find the digit in the rounding place. Then look at the next digit to the right.

So, 350 rounds to 400. Donna has about 400 rocks

**Explain It**

Question 1.

If you round 350 to the nearest ten, would you still say that Donna has about 400 rocks? Why or why not?

Answer:

Question 2.

Explain why 350 is the least number that rounds to 400.

Answer:

**One Way**

You can use a number line.

394 is closer to 390 than 400,

so 394 rounds to 390.

Tito has about 390 rocks.

**Another Way**

You can use place value.

- Find the digit in the rounding place.
- Look at the next digit to the right. If it is 5 or greater, increase the digit in the rounding place by 1. If it is less than 5, leave the rounding digit alone.
- Change all digits to the right of the rounding place to 0.

So, 394 rounds to 390.

Tito has about 390 rocks.

**Guided Practice**

**Do you know HOW?**

Round to the nearest ten.

Question 1.

37

Answer:

Question 2.

63

Answer:

Question 3.

85

Answer:

Question 4.

654

Answer:

Question 5.

305

Answer:

Question 6.

752

Answer:

Round to the nearest hundred.

Question 7.

557

Answer:

Question 8.

149

Answer:

Question 9.

461

Answer:

Question 10.

207

Answer:

Question 11.

888

Answer:

Question 12.

835

Answer:

**Do you UNDERSTAND?**

Question 13.

**Number Sense** What number is halfway between 250 and 260?

Answer:

Question 14.

**Reasoning** Tito adds one more rock to his collection. Now about how many rocks does he have, rounded to the nearest ten?

rounded to the nearest hundred? Explain your answer.

Answer:

Question 15.

**Writing to Explain** Tell what you would do to round 46 to the nearest ten.

Answer:

**Independent Practice**

Round to the nearest ten.

Question 16.

45

Answer:

Question 17.

68

Answer:

Question 18.

98

Answer:

Question 19.

24

Answer:

Question 20.

55

Answer:

Question 21.

249

Answer:

Question 22.

732

Answer:

Question 23.

235

Answer:

Question 24.

805

Answer:

Question 25.

703

Answer:

Question 26.

Reasoning Round 996 to the nearest ten. Explain your answer.

Answer:

**Independent Practice**

Round to the nearest hundred.

Question 27.

354

Answer:

Question 28.

504

Answer:

Question 29.

170

Answer:

Question 30.

839

Answer:

Question 31.

682

Answer:

Question 32.

945

Answer:

Question 33.

585

Answer:

Question 34.

850

Answer:

Question 35.

702

Answer:

Question 36.

270

Answer:

Question 37.

**Reasoning** Round 954 to the nearest hundred. Explain your answer.

Answer:

**Problem Solving**

Question 38.

**Number Sense** Give a number that rounds to 200 when it is rounded to the nearest hundred.

Answer:

Question 39.

**Writing to Explain** Describe the steps you would follow to round 439 to the nearest ten.

Answer:

Question 40.

**Number Sense** If you are rounding to the nearest hundred, what is the greatest number that rounds to 600? What is the least number that rounds to 600?

Answer:

Question 41.

**Number Sense** A 3-digit number has the digits 2, 5, and 7. To the nearest hundred, it rounds to 800. What is the number?

Answer:

Question 42.

To the nearest hundred dollars, a computer game costs $100. Which could NOT be the actual cost of the game?

A. $89

B. $91

C. $95

D. $150

Answer:

Question 43.

What is the standard form of 700 + 40?

A. 740

B. 704

C. 470

D. 407

Answer:

Question 44.

There are 293 steps to the top of the Leaning Tower of Pisa in Italy. To the nearest hundred, about how many steps are there?

Answer:

**Algebra Connections**

**Greater, Less, or Equal**

Remember that the two sides of a number sentence can be equal or unequal. A symbol >, <, or = tells how the sides compare. Estimation or

reasoning can help you tell if one side is greater.

**Example:** 6 + 2 imgg 7 8 + 1

Think Is 6 + 2 more than 8 + 1?

Since 6 + 2 = 8, 8 is already less than 8 + 1. Write “< .”

6 + 2 8 + 1 Copy and complete. Replace the circle with >, <, or =.

Check your answers.

Question 1.

3 + 4 2 + 7

Answer:

Question 2.

9 + 1 5 + 4

Answer:

Question 3.

5 + 3 6 + 3

Answer:

Question 4.

2 + 9 1 + 8

Answer:

Question 5.

4 + 6 4 + 7

Answer:

Question 6.

8 + 6 9 + 5

Answer:

Question 7.

18 + 2 16 + 4

Answer:

Question 8.

15 + 5 10 + 8

Answer:

Question 9.

14 + 4 12 + 4

Answer:

Question 10.

17 + 3 20 + 1

Answer:

Question 11.

21 + 2 19 + 2

Answer:

Question 12.

27 + 3 26 + 4

Answer:

For 13 and 14, copy and complete each number sentence. Use it to help solve the problem.

Question 13.

Al and Jiro had some toy animals. Al had 8 lizards and 3 frogs. Jiro had 11 lizards and 2 frogs. Who had more toy animals?

Answer:

Question 14.

Look at the number of blocks that come in a set below. Val used all of the small and large cylinders. Jen used all of the small and large cubes. Who used more blocks?

Answer:

Question 15.

Write a Problem Write a problem using this number sentence:

9 + 2 > 4 + 5.

Answer: