## 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?
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?
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?

Question 2.
Explain why 350 is the least number that rounds to 400.

One Way
You can use a number line.

394 is closer to 390 than 400,
so 394 rounds to 390.

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.

Guided Practice

Do you know HOW?
Round to the nearest ten.
Question 1.
37

Question 2.
63

Question 3.
85

Question 4.
654

Question 5.
305

Question 6.
752

Round to the nearest hundred.
Question 7.
557

Question 8.
149

Question 9.
461

Question 10.
207

Question 11.
888

Question 12.
835

Do you UNDERSTAND?
Question 13.
Number Sense What number is halfway between 250 and 260?

Question 14.
Reasoning Tito adds one more rock to his collection. Now about how many rocks does he have, rounded to the nearest ten?

Question 15.
Writing to Explain Tell what you would do to round 46 to the nearest ten.

Independent Practice

Round to the nearest ten.
Question 16.
45

Question 17.
68

Question 18.
98

Question 19.
24

Question 20.
55

Question 21.
249

Question 22.
732

Question 23.
235

Question 24.
805

Question 25.
703

Question 26.

Independent Practice

Round to the nearest hundred.
Question 27.
354

Question 28.
504

Question 29.
170

Question 30.
839

Question 31.
682

Question 32.
945

Question 33.
585

Question 34.
850

Question 35.
702

Question 36.
270

Question 37.

Problem Solving

Question 38.
Number Sense Give a number that rounds to 200 when it is rounded to the nearest hundred.

Question 39.
Writing to Explain Describe the steps you would follow to round 439 to the nearest ten.

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?

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?

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

Question 43.
What is the standard form of 700 + 40?
A. 740
B. 704
C. 470
D. 407

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?

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

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 =.
Question 1.
3 + 4 2 + 7

Question 2.
9 + 1 5 + 4

Question 3.
5 + 3 6 + 3

Question 4.
2 + 9 1 + 8

Question 5.
4 + 6 4 + 7

Question 6.
8 + 6 9 + 5

Question 7.
18 + 2 16 + 4

Question 8.
15 + 5 10 + 8

Question 9.
14 + 4 12 + 4

Question 10.
17 + 3 20 + 1

Question 11.
21 + 2 19 + 2

Question 12.
27 + 3 26 + 4

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?

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?

Question 15.
Write a Problem Write a problem using this number sentence:
9 + 2 > 4 + 5.