6 — Rounding and Estimation

Rounding and Estimation

Solution & Explanation · ID: 8875B1BE

Question

Estimate the product of 38 × 21 using rounding.

Hint

Round both numbers to make them easier to multiply mentally.

Concept

To estimate a product using rounding, round each factor to a convenient place value, then multiply the rounded numbers.

Show Answer

800

Show Solution
1

Round 38 to the nearest ten: 40

2

Round 21 to the nearest ten: 20

3

Multiply the rounded numbers: 40 × 20

4

Calculate: 40 × 20 = 800

Visual showing original problem 38 × 21 with arrows pointing to rounded values 40 × 20. Below shows the multiplication 40 × 20 = 800 in large text. The rounding changes are highlighted: 38→40 and 21→20.