(10a + b)^2 = 100a^2 + b^2 + 2ab So... 73^2 is 4900 + 9 + 420 = 5329. The really nice part is getting estimates for square roots of numbers. So, sqrt(3895)? 6

(10a + b)^2 = 100a^2 + b^2 + 2ab So... 73^2 is 4900 + 9 + 420 = 5329. The really nice part is getting estimates for square roots of numbers. So, sqrt(3895)? 60^2 + 120n = 3600 + 120n => n=2; that's 3844 (from above); the difference is 51; the residual estimate is then: 62 51/(62*2).