don steward
mathematics teaching 10 ~ 16

Thursday, 19 January 2017

mirror multiplications

first a few examples indicating that 'mirror' multiplications do not usually have the same answers

but then sometimes they do...
253 x 64 = 46 x 352

further examples of mirror multiplications that do have the same answers

the powerpoint for this task includes a step by step calculation for 253 times 64

for mirror multiplications with the same solutions:

as an initial step to considering rules and why they work,  how can the lead and final digits of the two multiplications be made to be the same when they cannot be the same numbers?

for the number in the centre of the 3-digit number, a grid method (expanded) representation shows how equal answers are obtained for the examples above - what is their common property?

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