Posted by **B.B.** on Wednesday, June 10, 2009 at 12:11pm.

Here is the original question: Give an estimate for the following expression: 978*66. Is the exact answer going to be greater than or less than the estimate? Here is what I have: I rounded 978 to 1000 and 66 to 70. 1000*70=70,000 the actual answer was 978*66=64,448 so the estimation was greater than the actual answer. Did I do this problem right? I used the rounding technique. Thanks.

- Math -
**MathMate**, Wednesday, June 10, 2009 at 12:22pm
The answer is correct.

However, you may want to review your reasoning.

What you said

*I rounded 978 to 1000 and 66 to 70. 1000*70=70,000 the actual answer was 978*66=64,448 so the estimation was greater than the actual answer.*

seems to tell me that you conclude that you were over-estimating **after** calculating the exact answer, which is not what is intended.

You are expected to determine if you answer is over- or under-estimating **without** calculating the exact answer.

Your teacher may prefer to see a reasoning as follows:

"I rounded 978 to 1000 and 66 to 70. 1000*70=70,000. Since I rounded **up** both multiplicands, the estimation was greater than the actual answer.

Check: 70000>978*66=64,448"

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