Math Review1. 10 25

- 7 34

2. 3x - 7 = 53 3. Simplify4432

4. Estimate 5.42 + 6.59 to the nearest tenth.

5. Which of the following statement is true about this graph?

a. These students spend more time at school than doing anything else.b. These students spend equal amounts of time on homework and watching t.v.c. These students spend equal amounts of time on homework and doing chores.d. These students spend less time playing outside than doing chores.

Answer Key

1. 2 13/20

2. x=20

3. 1 3/8

4. 5.4 + 6.6 = 12.0

5. c

Estimation Objective: I can make estimates using

whole numbers, decimals, and fractions.

3.87 ≈ 4 7 ≈ 82

3

Essential Questions

1. What is estimation? How should you use it to determine the reasonableness of your answer?

2. What is estimation? Why should you use it to determine the reasonableness of your answer?

3. What is estimation? When do I use it?

4. What is rounding? Why is it important to estimation?

Adding & Subtracting Estimation

You can estimate an answer before you calculate, to make sure your answer is reasonable.

The symbol ≈ means “is approximately equal to.”

Check It Out...

Estimating Decimals

1. Find the place value you want (the "rounding digit") and look at the digit just to the right of it.2. If that digit is less than 5, do not change the rounding digit but drop digits to the right of the decimal.

3. If that digit is greater than or equal to five, add one to the rounding digit and drop digits to the right of the decimal.

Let’s Try It!Estimate the following to the given place value:

74.29 to the nearest tenth50.009 to the nearest hundredth69.45898 to the nearest thousandth203.978 to the nearest hundredth

74.350.01

69.459203.98

Now Try These!Estimate to the nearest

hundredths place...then solve.

84.034 - 32.982

345.0285 + 272.9762

581.236 - 87.2346

84.03 - 32.98 =51. 05

345.03 + 272.98 =72. 05

581.24 - 87.23 =494.01

Estimating with Fractions

Sometimes it is better to round a fraction to the nearest half in order to estimate an addition or subtraction problem…

For Example

0 ½ 1

35

Draw a number lineDivide the line up into equal

portions of your denominator’s value

Decide whether it is closer to a whole or a half

35

15

25

It is closer to ½

Let’s Try a Couple...

0 ½ 1

67

27

17

37

47

57

67

It is closer to 1

Draw a number lineDivide the line up into equal

portions of your denominator’s value

Decide whether it is closer to a whole or a half

Estimating Mixed Numbers

Is 5 closer to 5, 5½, or 6?38

5 5½ 6

Draw a number lineDivide the line up into equal

portions of your denominator’s valueDecide whether it is closer to a

whole or a half

3852

85185

Round these mixed numbers to the nearest half…

2 4 9

12 59

5 811

6 913

2 32½

12 1312½

5 65½

6 76½

Round Each Fraction to Add and Subtract

716+ 13

7 423+

945 - 62

9 258-

7 + 1½ + 5 = 13½

10 - 6 - 3 = 1

Remember...Estima

te first!

Now Let’s Estimate! Jack has some 24

pieces of licorice rope. He gives 2 and 3/4 pieces to Jill, 6 and 5/9 to Jim, and 9 and 9/11 to June. How much does he have left for himself?

Remember...Estima

te first!

3 +6½ +10 = 19½24 - 19½ = 4½

Now You Try It!Jennifer ordered two pizzas to share with her friends. She gives Jeff 3/8 of the pizza and her girlfriends eat 7/8 of the pizza. How much pizza will she have left for herself?

2 - ½ - 1½ = ½

Closure

On a sticky note describe the process of estimating with decimals or fractions.

Independent Practice Estimation1. Estimate to the nearest

tenth..23.49 + 34.78

579 + 31

7 835+ =

2. Estimate to the nearest hundredth..

54.938 + 160.7813. Estimate to the nearest dollar..$59.10 - $23.91

4. 9 47

6 45

Is closer to 9, 9½, or 10?

5.Is closer to 6, 6½, or 7?

6.

7. 923 - 14

7 358- =

8. Amanda has some 16 candy bars. She gives 4 and 3/4 bars to William, 3 and 3/9 to Orrin, and 2 and 1/11 to Athena. How much does she have left?

Answer Key

1. 23.5 + 34.8 = 58.3

2. 54.94 + 160.78 = 215.72

3. $59 + $24 = $83

4. 9 1/2

5. 7

6. 6 + 3 + 8 1/2 = 171/2

7. 10 - 1 1/2 - 3 1/2 = 5

8. 16 - 5 - 3 - 2 = 7