how can we do estimate the sum ?
we get the estimate by rounding here .
1. For numbers with two digits, there can only be one estimate because you can only round to the tens place
Forexample, estimate the following sums:
36 + 21, 74 + 15, and 85 + 24
36 + 21 = 40 + 20 = 60
74 + 15 = 70 + 20 = 90
85 + 24 = 90 + 20 = 110
2. For numbers with three digits, you can get two estimates
For example, estimate the following sums:
176 + 432, 250 + 845, and 986 + 220
Rounding 176 and 432 to the nearest hundred, gives 200 + 400 = 600
However,rounding 176 and 432 to the nearest ten , gives 180 + 430 = 610
The exact answer is 176 + 432 = 608. Notice that 610 is closer to 608 than 600, so rounding to the nearest 10 gives a better estimate
Rounding 250 and 845 to the nearest hundred gives 300 + 800 = 1100
Moreover, rounding 250 and 845 to the tens gives 250 + 850 = 1100
The exact answer is 250 + 845 = 1095. Notice this time, However, that you get the same answer
So, in this way we get the estimate figure.