3. Writing to Explain Use rounding to estimate the product
13 ! 9. Then, use compatible numbers to find the actual
answer. If Alison was rounding to find how much 13 books
that were $9 apiece cost, would she get a good estimate?
Explain
If I were rounding, I'd estimate 13 * 10 = a little less than $130.
34×4
6×33=198
50
To estimate the product of 13 and 9 using rounding, you would round each number to the nearest whole number. In this case, 13 is already a whole number, so it remains the same. However, 9 would be rounded up to 10 since it is closer to 10 than to 0.
So, the estimated product of 13 and 9 would be 13 x 10 = 130.
To find the actual answer using compatible numbers, you would look for numbers that are close to 13 and 9 that would make the multiplication easier. In this case, the compatible numbers would be 10 and 9 because they are near to the numbers being multiplied.
Using compatible numbers, the actual product can be found by multiplying 10 and 9:
10 x 9 = 90
Now, let's compare the estimate (130) to the actual product (90).
Alison would not get a good estimate by rounding to find how much 13 books that were $9 apiece cost. The estimate of 130 is significantly higher than the actual cost of 90. So, it is not a good approximation in this case.