Okay, then, here's an example of squaring a two digit number ending in 4.
642 = ????
I'd know this anyway, from the old familiar progression of 1, 2, 4, 8, 16 ... but for the purpose of this exercise, I have never had to work out 642 in my life before.
64 x 64 ==> ((64 + 4) x (64 - 4)) + 42
==> (68 x 60) + 16
==> (680 x 6) + 16
==> 4080 + 16
==> 4096.
Can you see how this process also works for 34 and 74 alike? :)
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branchandroot
All The Fours
Date: 2009-06-26 08:37 pm (UTC)642 = ????
I'd know this anyway, from the old familiar progression of 1, 2, 4, 8, 16 ... but for the purpose of this exercise, I have never had to work out 642 in my life before.
64 x 64 ==> ((64 + 4) x (64 - 4)) + 42
==> (68 x 60) + 16
==> (680 x 6) + 16
==> 4080 + 16
==> 4096.
Can you see how this process also works for 34 and 74 alike? :)