Estimating Products

Use Compatible Numbers… When estimating fractions you can use 2 different strategies. Use Compatible Numbers… …when multiplying a whole number and a fraction. …when multiplying a mixed number and a fraction. 65 3 x 7 16 3 3 x 5 4

Use Compatible Numbers… When estimating fractions you can use 2 different strategies. Use Compatible Numbers… …when multiplying a whole number and a fraction. …when multiplying a mixed number and a fraction. Use Rounding… …when multiplying two mixed numbers. …when multiplying a mixed number and a whole number. 17 2 4 9 x 65 7 3 10 x 7 5 2 x 1 16 3 3 x 2 5 4

Whole Number X Fraction When to Use What... Type of Problem Example Best Strategy Whole Number X Fraction 5 6 41 x Compatible Numbers

41 35 42 ≈ 5 x 6 5 x 6 Estimation with Compatible Numbers 42 ÷ 6 = 7 When estimating a product of a fraction and a whole number, use compatible numbers. 41 35 5 ≈ x 6 42 5 42 ÷ 6 = 7 x 7 x 5 = 35 6 Step 1: Find the closest basic math fact to 6 and 41. Step 2: Rewrite the problem with the compatible numbers. Step 3: Divide the whole number by the denominator. Step 4: Multiply the quotient by the numerator.

Whole Number X Fraction Mixed Number X Fraction When to Use What... Type of Problem Example Best Strategy Whole Number X Fraction 5 6 41 x Compatible Numbers Mixed Number X Fraction 5 7 x 13 2 9 Compatible Numbers

10 13 14 ≈ x x 2 5 9 7 5 7 Estimation with Compatible Numbers 14 ÷ 7 = When estimating a product of a fraction and a mixed number, use compatible numbers. 10 13 5 2 ≈ x 7 9 14 14 ÷ 7 = 2 5 x 2 x 5 = 10 7 Step 1: Find the closest basic math fact to 7 and 13 . Step 2: Rewrite the problem with the compatible numbers. Step 3: Divide the whole number by the denominator. Step 4: Multiply the quotient by the numerator. 2 9

41 13 10 x x x When to Use What... 5 6 5 2 7 9 2 1 3 9 Type of Problem Example Best Strategy Whole Number X Fraction 5 6 41 x Compatible Numbers Mixed Number X Fraction 5 7 x 13 2 9 Compatible Numbers Mixed Number X Mixed Number 10 2 3 x 1 9 Round

When estimating a product of mixed numbers, use rounding. Estimation with Rounding Think: Think: 2 3 1 2 1 9 1 2 V V Add 1 More! Just Ignore! 3 10 2 1 x 3 9 When estimating a product of mixed numbers, use rounding. 11 3 33 x =

When to Use What... Type of Problem Example Best Strategy Whole Number X Fraction 5 6 41 x Compatible Numbers Mixed Number X Fraction 5 7 x 13 2 9 Compatible Numbers Mixed Number X Mixed Number 10 2 3 x 1 9 Round Whole Number X Mixed Number x 4 3 7 Round

7 4 5 7 35 3 x 4 x = Estimation with Rounding V Add 1 More! Think: 3 4 1 2 V Add 1 More! 7 4 3 x 4 When estimating a product of a mixed number and a whole number, use rounding. 5 7 35 x =

41 13 10 4 7 x When to Use What... 6 5 2 9 1 3 Best Strategy Example Type of Problem Round Whole Number X Mixed Number Mixed Number X Mixed Number Compatible Numbers Mixed Number X Fraction Whole Number X Fraction

More Examples

32 12 30 ≈ 2 x 5 2 x 5 Estimation with Compatible Numbers 30 ÷ 5 = 6 When estimating a product of a fraction and a whole number, use compatible numbers. 32 12 2 ≈ x 5 30 2 30 ÷ 5 = 6 x 6 x 2 = 12 5 Step 1: Find the closest basic math fact to 5 and 32. Step 2: Rewrite the problem with the compatible numbers. Step 3: Divide the whole number by the denominator. Step 4: Multiply the quotient by the numerator.

When estimating a product of mixed numbers, use rounding. Estimation with Rounding Think: Think: 3 8 1 2 7 9 1 2 V V Just Ignore! Add 1 More! 8 4 3 7 x 8 9 When estimating a product of mixed numbers, use rounding. 8 5 40 x =

41 35 42 ≈ 5 x 6 5 x 6 Estimation with Compatible Numbers 42 ÷ 6 = 7 When estimating a product of a fraction and a whole number, use compatible numbers. 41 35 5 ≈ x 6 42 5 42 ÷ 6 = 7 x 7 x 5 = 35 6 Step 1: Find the closest basic math fact to 6 and 41. Step 2: Rewrite the problem with the compatible numbers. Step 3: Divide the whole number by the denominator. Step 4: Multiply the quotient by the numerator.

Closest Basic Math Fact Review: Compatible Numbers Compatible numbers allow you to estimate quotients by changing the dividend and the divisor into a basic math fact. Division Problem Closest Basic Math Fact Estimation 98 ÷ 9 99 ÷ 9 = 11 55 ÷ 8 56 ÷ 8 = 7 29 ÷ 7 28 ÷ 7 = 4 40 ÷ 6 42 ÷ 6 = 7 11 ÷ 3 12 ÷ 3 = 4

7 5 5 8 2 4 3 9 Rounding Fractions V V Find you’re your number, Look right next door , just ignore, or more, add one more. Think: Think: 1 2 Less than Four or less 2 3 4 9 1 2 1 2 V V 1 2 Five Just Ignore! Add 1 More! 7 5 5 8 2 4 3 9