Front end estimation is a way of estimating the sums or differences of numbers by rounding. In this method, we first round each number and then add or subtract the leftmost place values. For example, to add 57+ 43, the front-end estimation is 40 + 60 = 100 when we round each number. The same method is used if we were to subtract 57 - 43. You can find more information here: .