Estimating Sums & Differences

1. Estimating Sums & Differences

2. Warm-Up Find the value of each expression. • 4.7 + 5.08 • 10 – 3.58

3. VOCAB • Rational Number: • a fraction made from integers • Sum: • ADD • Difference: • Subtract • Rounding: • Choose easy #’s close to hard #’s.

4. 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 #)

5. 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 _________

6. 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

7. 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

8. Example 2a Estimate the value of . • Each fraction is less than 1 unit from zero so round to the nearest .

9. Example 2b Estimate the value of . • Each fraction is more than 1 unit from zero so round to the nearest integer.

10. 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?

11. Communication Prompt Describe a time when you used estimating in a situation outside of math class.