Seven times tables...

I get stuck on a few. Because of the terrible rote learning technique employed by my parents, half my times table memory (not half, but some of the bigger numbers) are currently wiped out and I have to rebuild.

63 is 7x9 because all the 9xs digits, add to 9.
42 is easy to remember because it also adds to 6.
21 adds to 3.

So basically 3, 6, 9 times 7, all add up their digits. So that is easy to remember.

The 4s and 8xs are all EVEN numbers.
so 28 = 7 x 4, 56 = 8 x 7.
8/2 is 4, so that is easy to remember.

So the hardest is 8 x 7. I can remember that 8 + 7 = 15. And then I take that 5, and take that 1, 1+5 = the last digit, and 1x5 = the first digit, so 56

So if I see 56, i can remember 15, and what adds to 15? Cant be less than 5, can't be 6 because of the 9xs table pattern, so its 7, or 8. 7x8.

And... 49 is 7x7
6x6 = 36 and incidentally 4x9 also =36...

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