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# Estimating Sums & Differences PowerPoint PPT Presentation

Estimating Sums & Differences. Warm-Up. Find the value of each expression. 4.7 + 5.08 10 – 3.58. VOCAB. Rational Number: a fraction made from integers Sum : ADD Difference : Subtract Rounding : Choose easy #’s close to hard #’s. Estimating. Decimals less than one

Estimating Sums & Differences

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#### Presentation Transcript

Estimating Sums & Differences

Warm-Up

Find the value of each expression.

• 4.7 + 5.08

• 10 – 3.58

VOCAB

• Rational Number:

• a fraction made from integers

• Sum:

• Difference:

• Subtract

• Rounding:

• Choose easy #’s close to hard #’s.

Estimating

Decimals

• less than one

• round to 0, 0.5 or 1

• more than one

• round to the nearest integer (whole #)

Fractions

• less than one

• round to 0, ½ or 1

• mixed numbers

• round to the nearest integer (whole #)

### Let’s Try Some Rounding…

• 0.2 rounds to ________

• 0.4 rounds to ________

• 0.7 rounds to ________

• 0.75 rounds to ________

• 1.6 rounds to ________

• ¼ rounds to _________

• 1/3 rounds to _________

• 3/5 rounds to _________

• 1 ¾ rounds to _________

### Example 1a

Estimate the value of – 4.23 + 2.8.

• Both numbers are more than one and should be rounded to nearest integer.

• – 4.23 → – 4

• 2.8 → 3

• – 4 + 3 = –1

• – 4.23 + 2.8 ≈ –1

### Example 1b

Estimate the value of 0.94 – (–0.43).

• Both numbers are less than one unit away from zero and should be rounded to the nearest 0.5.

• 0.94 → 1

• – 0.43 → – 0.5

• 1 – (–0.5) = 1 + 0.5 = 1.5

• 0.94 – (–0.43) ≈ 1.5

### Example 2a

Estimate the value of .

• Each fraction is less than 1 unit from zero so round to the

nearest .

### Example 2b

Estimate the value of .

• Each fraction is more than 1 unit from zero so round to the nearest integer.

Estimate the value of each expression.

• 3.21 + 6.3

• 0.13 – 0.925

• Matt bought pounds of apples, pounds of grapes and pounds of potatoes. How many pounds did he buy?

### Communication Prompt

Describe a time when you used estimating in a situation

outside of math class.