Multiplying by multiples of ten (3rd grade math)

First, I show how to multiply a number by ten, there is a shortcut: just tag a zero to the number. For example, 10 × 56 is 56 and a zero tagged... 560. Then we look at a rectangle and its area...and from there, go to study multiplications such as 3 × 40 or 7 × 90. For these there is a shortcut, too! For example, 7 × 90 equals 7 × 9 × 10, and in that, we can multiply 7 × 9 = 63 first, so the problem becomes 63 × 10 which equals 630.

See also

Area of Compound Shapes — a video lesson

Math Mammoth Grade 3 curriculum

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