Estimating Decimal Products

by Moris
(Ft.StockonTx)

How do I estimate the problem 10.78x1044.3092

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Oct 05, 2010
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by: Karin

Estimating is always tricky because you want to get as close to the correct answer as possible, but you also need to compute pretty quickly.

The fastest and easiest way to estimate the answer is to round 10.78 down to 10 because multiplying by 10 is easy! (Just add a 0 to the end of the number you are multiplying).

Round 1044.3092 to 1044, so:

10 * 1044 = 10440.

If you want to get a little closer to the correct answer, 10.78 is actually closer to 11. Multiplying by 11 is a little harder, but we could think of it as:
10(1044) + 1(1044)
10440 + 1044 = 11484.

So, you still multiply by 10 which is easy, but then you have to add another 1044. That can be a little more difficult using mental math,but your answer is closer to the actual answer.

I hope this helps!

Karin

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