Estimating and Assessing the Reasonableness of Multiplying Fractions

This lesson teaches how to assess the reasonableness of a product by estimating. It explains how to determine which whole number a fraction is closest to and use that for estimation. Several examples are provided, including multiplying 2 by 3/4, 3 by 5/3, 5 by 4/5, and 2 by 18/10. The lesson emphasizes using number lines and visual models to understand the estimation process and verify the reasonableness of the calculated product.

What is the first step in determining if a product is reasonable when multiplying a whole number by a fraction?

• Multiply the numbers directly.

• Find the closest whole number to the fraction.

• Divide the whole number by the fraction.

• Add the fraction to the whole number.

When estimating 5 times 4/5, which whole number is 4/5 closest to?

• 2

• 1

• 0

• 5

What is the estimated product of 5 times 4/5?

• 4

• 6

• 5

• 3

How do you estimate the product of 2 times 18/10?

• Multiply 2 by 2.

• Multiply 2 by 1.

• Multiply 2 by 3.

• Multiply 2 by 0.

What is the result of multiplying 2 times 18/10 using an area model?

• 3 and 6/10

• 5

• 4

• 2 and 8/10