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Identify the Best Regrouping

publish date: 2026/05/10 01:12:8.747788 UTC

volume_mute

Which regrouping makes \(5 \times 18 \times 20\) easiest to compute?

\((5 \times 18) \times 20 = 90 \times 20\)

\(5 \times (18 \times 20) = 5 \times 360\)

\((5 \times 20) \times 18 = 100 \times 18\)

All three are equally easy.

Correct Answer

\((5 \times 20) \times 18 = 100 \times 18\)

Explanation

Pairing 5 and 20 gives \(100\) — a power of 10. Then \(100 \times 18 = 1{,}800\) requires only attaching two zeros. This is the most efficient application of the associative property.

Reference

go-math-science.com

Quizzes you can take where this question appears

Use properties of multiplication to multiply whole numbers