SQUARING ANY TWO-DIGIT NUMBERS.

Is it really so simple to square a two-digit number?

Yes, it can with the following technique and some practice. Furthermore, it doesn’t matter if you originally round up or down.

Let’s say I wanted to square 13 as an example.

As opposed to 13 times 13, I took away 3 to get 10, which I rounded down to 10, and I also added 3 to get 16, which I rounded up to 16.

Next, added the square of three to the result of 16 x 10 = 160.

i.e. 160 + 3² = 160 + 9

= 169 is the answer.

Let’s try another problem. Calculate 56² in your head before looking at how we did it, below:

 SECRET:

Always round up or down to the nearest multiple of 10. 

So, if the number to be squared ends in 6, 7, 8, or 9, round up, and if the number to be squared ends in 1, 2, 3, or 4, round down. (If the number ends in 5, do both!)

With this strategy we will add only the numbers 1, 4,9, 16, or 25 to the first calculation.