The calculation of the square root, relies on this result from squaring a number N = 10d + e (that is, single digits d and e, but d is in the 10s place): NN =

The calculation of the square root, relies on this result from squaring a number N = 10d + e (that is, single digits d and e, but d is in the 10s place): NN = (10d + e)(10d + e) = 100dd + 20de + ee Group the digits of the square by two, and add extra values to the "divisor" so that the extraction of the square root in effect undoes the squaring above. See, for example, https://sciencing.com/calculate-square-root-hand-5081134.html https://sciencing.com/calculate-square-root-hand-5081134.htm...