Math fun: If you want to square any two digit number more quickly than the traditional algorithm, here’s a strategy. It does require you to know the squares of all the single-digit numbers, as well as a bit of mental juggling.
First, if the number ends in a zero, square the first digit and put 00 after it. 60^2 = 3600.
If the number ends in five, square the first digit, add it to itself, and put 25 after it. 6^2 + 6 = 42, so 65^2 = 4225.
For all other numbers, use the closest multiple of 5 as above. That means you’ll need to use the difference of squares formula, but it’s not that difficult if the difference is one or two.
Let’s say it’s 1: Add your target to the neighboring multiple of five, then add or subtract the result from the squared multiple of five. Since 65^2 = 4225, 64^2 = 4225 – 129 = 4096 and 66^2 = 4225 + 131 = 4356.
Let’s say it’s 2: Do the same addition but double the result before adding or subtraction. 63^2 = 4225 – 128*2 = 4225 – 256 = 3969 and 67^2 = 4225 + 132*2 = 4489.
(This will also work for numbers over 100, but it’s probably confusing enough as it is.)