Question

Estimate decimals sums and differences

Answer 1

First basically solve.
Next, take the number after the decimal point and see if it's larger than 5 or lesser than 4.
Than, Look at the number before the decimal point and relate back to step 2 (Next) if the number is higher than one. Add by 1 to the number before the decimal.
Example:
4.45
vvvv

4.(4)5 > The 4 is lesser than 4, so the number before the decimal point is keep the same.
vvvvvvv
Answer: 4

Answer 2

By using benchmarks to estimate,

5. The estimated sum of 2.81 + 3.72 is 7.

6. The estimated sum of 12.54 + 7.98 is 21.

How to estimate the sums of decimals using benchmarks

To estimate the sums of decimals using benchmarks, round the decimals to the nearest whole number and then perform the addition. Let's estimate the following sums:

2.81 + 3.72:

2.81 to the nearest whole number is 3.

3.72 to the nearest whole number is 4.

Adding these rounded numbers, we have 3 + 4 = 7.

Therefore, the estimated sum of 2.81 + 3.72 is 7.

12.54 + 7.98:

12.54 to the nearest whole number is 13.

7.98 to the nearest whole number is 8.

Adding these rounded numbers, we have 13 + 8 = 21.

Therefore, the estimated sum of 12.54 + 7.98 is 21.