What is #52 * 81#?

1 Answer
Apr 9, 2016



A quick way to check mathematical calculations is to round the numbers. Using 50 for 52 and 80 for 81, the much easier 50 x 80 = 4000 gives you an “order of magnitude” check on your calculations.

To do a specific multiple-place multiplication we multiply one number by the LAST ('ones' position) number first, then multiply it by the next ('tens' position) number, SHIFTING the first value to the 'ones', 'tens', 'hundreds' column as we progress. Any size of numbers can be calculated manually in this way.
So, for this problem we set up
x 52

then the first number is 2 x 81, put directly below the numbers, and the second number is 5 x 81 placed under the first calculation, shifted one column to the left. Finally, we ADD this set of numbers to arrive at the final answer.
# x ul52 #
# 162 # (this formatting is garbage - no space or tab! :P )