So, to do this we'll be using rounding instead of compatible to estimate.
To begin, do 271 + 425
By rounding a hundred, you would do
300 + 400 = 700 as the estimated sum.
By rounding tens, you would do
270 + 430 = 700 as estimated sum.
In this case, either one can be done which means 700 is the best estimated sum.
