Estimate sums and differences of decimals
Learn with an example
Estimate the sum by rounding each number to the nearest whole number and then adding.
9.78 + 3.49
The sum is approximately_________
Round each number to the nearest whole number.
9.78 + 3.49 = ?
10 + 3 = ?
Now add:
10 + 3 = 13
The sum is about 13.
Estimate the sum by rounding each number to the nearest whole number and then adding.
5.01 + 1.98
The sum is approximately _________.
Round each number to the nearest whole number.
5.01 + 1.98 = ?
5 + 2 = ?
Now add:
5 + 2 = 7
The sum is about 7.
Estimate the sum by rounding each number to the nearest whole number and then subtracting.
9.78 − 3.49
The difference is approximately_________
Round each number to the nearest whole number.
9.78 − 3.49 = ?
10 − 3 = ?
Now subtract:
10 − 3 = 7
The difference is about 6.
Estimate the sum by rounding each number to the nearest whole number and then subtracting.
9.21 − 3.69
The difference is approximately_________
Round each number to the nearest whole number.
9.21 − 3.69 = ?
9 − 4 = ?
Now subtract:
9 − 4 = 5
The difference is about 5.
Let’s practice!
