4 ms·
Assuming one's memorized a table of squares already. 10^2 = 100 11^2 + 13^2 = 121 + 169 = 290 12^2 + 14^2 = 144 + 196 = 340 100 + 290 + 340 = 730 730 / 365
by delhanty 7y ago
Assuming one's memorized a table of squares already.
10^2 = 100
11^2 + 13^2 = 121 + 169 = 290
12^2 + 14^2 = 144 + 196 = 340
100 + 290 + 340 = 730
730 / 365 = 2
- lonelappde 7y agoYou can also "walk it up" if you haven't memorized them: 10^2*5 + (10+11)*4 + (11+12)*3 + (12+13)*2 + (13+14) ------------ 500 + 84 + 69 + 50 + 27 ----- 730 It's a bit of detail to juggle in your head but not too bad if you hang on to your current subtotal and remember where you are in the sequence to compute the next addend, and you know it's easier to add multi-digit numbers left-to-right than-right to-left. You only carry from the ones place twice.