Math Hack #1: Squaring 2-digit numbers

In this section we will cover some techniques for speeding up our math.

The faster we can think, the faster we can absorb new material and the faster we can write our exams.
It also allows us to do a sanity check that the calculations we have been doing are in the right ball park.

Today: Tell me - right now - what’s 35 x 35?

We’ll cover the method of squaring any 2 digit number that ends in 5:

1. Take the first digit and multiply it by the next higher digit -

so take 3x4 and this gives us 12;

2. Now attach 25 to the end of the 12,

and we get 1225.

35x35 = 1225.

Now, try this with:

• 45x45

• 85x85

• 55x55

How quick is that once you know how to do it?