Step-by-step explanation: To estimate the sum of two decimals, first round each decimal to the nearest unit. Finally, you will simply add and you will get your answer.
I'll show an example.
Estimate the following sum.
4.94 + 2.185
To estimate the sum of two decimals such as 4.94 + 2.185, first round each number to the nearest unit.
To round 4.94 to the nearest unit, we see that 4 is in the rounding place so we look at the digit to the right of the 4. The 9 in this position tells us to round up which means we add 1 to the 4 in the rounding place to get 5 and we change all digits to the right of the rounding place to 0. So 4.94 rounds up to 5.00 or just 5.
To round 2.185 to the nearest unit, we see that 2 is in the rounding place so we look at the digit to the right of the 2 which is 1. The 1 in this position tells us to round down. This means that 2 in the rounding place stays the same, and we change all digits to the right of the 2 to 0. So 2.185 rounds down to 2.000 or just 2.
Now we simply add 5 + 2 to get a sum of 7.
Therefore, 4.94 + 2.185 is approximately 7.
