Once you know one small multiplication fact, patterns let you estimate huge ones in your head.
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Students will estimate products and quotients using patterns: round one factor, or the divisor, to its greatest place value, then multiply or divide a short string of easy facts to reach the estimate.
For multiplication, round the larger factor and leave a one-digit factor alone, then build a pattern by multiplying the small fact by ten each step. For division, round the divisor first and swap the dividend for a nearby number that divides evenly.
Rounding the dividend before the divisor in a division problem gets the steps backwards. It also helps to say the pattern's easy fact out loud before multiplying zeros onto it, rather than jumping straight to the big number.
Give him a two- or three-digit multiplication problem from a grocery receipt or a sports stat and have him build the pattern by hand before checking it on a calculator.
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Before You Start
The words this lesson uses. Tap a card to see what it means, then come back to them whenever a question uses one.
Part One
Questions about the story you just read. Pick your answer straight off, or press Find it in the story if you would rather hunt for the sentence first.
Part Two
The word cards are at the top of this page. Look back at them as often as you need, then answer.