Question

4+8+12+......+2000=?

Answer 1

4:2=2
8:2=4
12:2=6
........
2000:2=1000

Answer 2

$\displaystyle 4+8+12+...+2000=4(1+2+3+...+500)= \\ \\ =4 \times \frac{500(500+1)}{2} =4 \times \frac{500 \times 501}{2} =4 \times \frac{250500}{2} = \\ \\ =4 \times 125250=501000$