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.
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"
Yes, you did the problem correctly using rounding to estimate the expression.
To estimate the product of 978 multiplied by 66, you rounded 978 to the nearest thousand which is 1000, and 66 to the nearest ten which is 70. Then, you performed the estimation calculation by multiplying these rounded numbers together, which gives you 1000 multiplied by 70 equal to 70,000.
The exact answer for 978 multiplied by 66 is 64,448. Since 70,000 is greater than 64,448, the estimation you calculated using rounding is greater than the actual answer for the expression.
Overall, you applied the rounding technique correctly and your reasoning is accurate. Well done!