4 ms·
FOIL it :) 40 * 60 + 40 * 8 + 60 * 7 + 7 * 8 Basically a bunch of single digit multiplies followed by stacking zeroes
by gretch 6y ago
FOIL it :)
40 * 60 + 40 * 8 + 60 * 7 + 7 * 8
Basically a bunch of single digit multiplies followed by stacking zeroes
- oh_sigh 6y agoOr 47x68= (50-3)x(70-2)=50x70 - 50x2 - 3x70 + 3x2
- ajkjk 6y agoMy mental method is not quite FOIL, for what it's worth. I distribute over one of the numbers -- so 47 * 68 = 47 * 60 + 47 * 8, and then compute the compute those (2400 + 420 = 2820). Then I grab additional terms: 2820 + 40 * 8 = 3140. 3140 + 7 * 8 = 3196 Among other things this scales better to larger numbers. I use it because it's more 'linear' -- I only need to remember one accumulated number at a time.