1+2+3+4+5+6+7+8+9+10 = 55
What is the Fastest way to do that?
The general "formula" for the sum of the first "n" positive integers is given by:
n(n + 1) / 2 ...so we have.....for the first 10 integers....
(10)(11)/2 = 110/2 = 55
1+2+3+4+5+6+7+8+9+10 = 55 What is the Fastest way to do that?
$$\small{\text{$1+2+3+4+5+6+7+8+9+10 =\dbinom{n+1}{2} = \dbinom{10+1}{2} = \dbinom{11}{2} = \dbinom{11}{9}=\dfrac{10\cdot 11}{2} = 5\cdot 11 = 55$}}$$