Things to Remember…

• Decide which method of estimation to use. Base your choice on the operation you will be using to calculate your estimate.

• Use the symbol which means “approximately equal to”

Estimate or Exact?

Suppose you are writing a news article. Your notes contain some data that may be estimates. For each situation, decide whether you have an estimate or an exact value. Explain your decision. a) The population of Florida is 16,000,000.b) Florida has 25 representatives in the U.S. House of Representatives.

Other examples??

Estimate

Exact Value

Estimating• Suppose you went food shopping with your parents this

weekend and bought Lucky Charms for $3.21, a frozen pizza for $4.79, Pepsi for $1.99, and a pack of gum for $1.15. Estimate the total cost of your purchases.

Step 1: Add the front-end digits

$3.21

$4.79

$1.99

+$1.15

$9

Step 2: Estimate the total amount of cents to the nearest dollar.

$3.21

$4.79

$1.99

+$1.15

$2

About $1

About $1

The total cost is about $11 (9 + 2).

Estimating• It took 75.75 pounds of shredded cheese to make the

world’s largest burrito. Estimate how many 10 pound boxes of shredded cheese the cooks needed.

75.75

10Set up the Quotient

80

10

Since the divisor does not need rounded to the leading digit choose the compatible number 80 for the dividend.

You will need about 8 ten pound boxes.

A rectangular kitchen is 8.5 ft long and 5.75 ft wide. Estimate

the area of the kitchen in square feet.

EstimatingEstimating

9 6 = 54 Multiply.

8.5 9

5.75 6Round each factor to the nearest whole number.

The area of the kitchen is about 54 ft2.

1-1

Extra Practice

Estimate.

1) 4.9 x 12.2 2) 2) 6.07 x 3.29 3) 3) 7.65 x 5.33 4) 4) 25.123 x 4.79

5 x 12 606 x 3 18

8 x 5 40

25 x 5 125

Extra Practice

Estimate.

1) 5.43 + 2.672) 8.09 + 11.24 3) 7.18 + 5.89 4) 3.62 + 2.31

Extra Practice

Estimate.

1) 5.43 + 2.67 5 + 2 = 7 .43 + .67 1 2) 8.09 + 11.24 8 + 11 = 19 .09 + .24 (not enough for 1)3) 7.18 + 5.89 7 + 5 = 12 .18 + .89 14) 3.62 + 2.31 3 + 2 = 5 .62 + .31 1

About 8 (7 + 1)About 19 About 13 (12 + 1)About 6 (5 + 1)

Extra Practice

Estimate.

1) 78.5 ÷ 8.8 2) 19.45 ÷ 4.92 3) 103.6 ÷ 9.72 4) 32.2 ÷ 7.56

Extra Practice

Estimate.

1) 78.5 ÷ 8.8 81 ÷ 92) 19.45 ÷ 4.92 20 ÷ 53) 103.6 ÷ 9.72 100 ÷ 104) 32.2 ÷ 7.56 32 ÷ 8

About 9About 4About 10

About 4