2 ms·
You 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) ------------ 50
by lonelappde 7y ago
You 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.