Question

1+2+3+4+5+6+7+8+9+10...........+100= ??

Answer 1

1+2+3+...+100=
100*101/2=50*101=5050

Answer 2

$\displaystyle 1+2+3+4+5+6+7+8+9+10+...+100= \\ \\ = \frac{100(100+1)}{2} = \frac{100 \times 101}{2} = \frac{10100}{2} =5050$