Estimate products: word problems

Understanding Estimation

  • Definition: Estimation involves finding a number that is close to the exact amount. It is useful when exact numbers are not necessary or practical.
  • Purpose: Helps in making quick decisions and checking if answers are reasonable.

Estimation Strategies

  • Rounding: Adjust numbers to the nearest ten, hundred, or other place value to simplify multiplication.
    • Example: Estimate the product of 47 and 32 by rounding 47 to 50 and 32 to 30, then multiply 50 × 30 = 1500.
  • Compatible Numbers: Use numbers that are easy to work with, often multiples of 10.
    • Example: For 46 × 27, estimate by using 50 × 30 = 1500.
  • Front-End Estimation: Focus on the leading digits of the numbers.
    • Example: For 88 × 56, consider 80 × 50.

Solving Word Problems

  • Read Carefully: Identify what is being asked and the numbers involved.
  • Choose an Estimation Strategy: Decide whether to round, use compatible numbers, or front-end estimation.
  • Perform the Estimation: Apply the chosen method to get an estimated answer.
  • Check Reasonableness: Ensure the estimated answer makes sense in the context of the problem.

Example Problems

  1. Problem: You are buying packs of pencils. Each pack has about 25 pencils, and you want to buy 14 packs. Estimate the total number of pencils.
    • Estimation: Round 25 to 30 and 14 to 10. Estimate: 30 × 10 = 300 pencils.
  2. Problem: A library has 56 shelves, each holding about 18 books. Estimate the total number of books.
    • Estimation: Round 56 to 60 and 18 to 20. Estimate: 60 × 20 = 1200 books.

Learn with an example

Cindy bought 77 packages of biscuits. Each package had 8 biscuits. About how many biscuits did Cindy buy? Choose the better estimate.

  • 64
  • 640

Multiply:

77 × 8 = ?

Round the first factor to the nearest ten.

640 biscuits is the better estimate.

A chef prepared 31 plates of prawn. There were 47 prawn on each plate. About how many prawn did the chef prepare? Choose the better estimate.

  • 1,500
  • 1,100

Multiply:

31 × 47 = ?

Round each factor to the nearest ten.

1,500 prawn is the better estimate.

A biscuit factory produced 31 packages of biscuits. There were 39 biscuits in each package. About how many biscuits did the factory produce in all? Choose the better estimate.

  • 120
  • 1,200

Multiply:

31 × 39 = ?

Round each factor to the nearest ten.

1,200 biscuits is the better estimate.

Let’s practice!🖊️