171 +727 round it or compatible numbers to estimate the sum

171 is rounded to 200 as it is closest to 200 than 100
and 727 is rounded to 700 as it is closest to 700 than 800
when we add 200 and 700 we get the answer 900
The sum of 171 and 727 is:
171 + 727 = 898
and 898 is rounded to 900 as it is closest to 900 than 800.