ESTIMATION

4 7

+ 8 1

1 2 8

Let’s estimate the value of 47 + 81 to check the answer.

Strategy for Estimation

Question: 47 + 81 = ______

Step 1: Round off each number to the nearest ten.

Example: 47 50, 81 80

Step 2: Add both rounded off numbers. Example: 50 + 80 = 130

So, 47 + 81 130 The value of 47 and 81 is about 130.

Estimate the value of 84 - 42

84 80

42 40

80 – 40 = 40

84 – 42 40

The value of 84 – 42 is about 40.

Estimate the value of 64 X 3

Step 1: Round off to the nearest ten.

64 60

Step 2: Then multiply.

60 X 3 = 180

So, 64 X 3 180

The value of 64 X 3 is about 180.

Estimate the value of 267 X 7

Step 1: Round off to the nearest hundred.

267 300

Step 2: Then multiply.

300 X 7 = 2100

So, 267 X 7 2100

The value of 267 X 7 is about 2100.

Estimate the division operationQuestion: 372 ÷ 4 = _________Step 1: Think of two estimated values

(divisor) that are divisible by 4. In this problem, choose 360 and 400 which are estimated values of 372.

Step 2: Choose 360 instead of 400 because 372 is nearer to 360 than to 400.

Step 3: Carry out the division to get an estimated value.

360 ÷ 4 = 90So, 372 ÷ 4 90 The value of 372 ÷ 4 is about 90.