Question

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.

Answer 1

The answer is correct.

However, you may want to review your reasoning.

What you said
<i>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.</i>

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

You are expected to determine if you answer is over- or under-estimating <b>without</b> 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 <b>up</b> both multiplicands, the estimation was greater than the actual answer.
Check: 70000>978*66=64,448"