Question

evaluate 1+2+3+....+100.using this value find7+14+21+.....+700.
plzz quick

Answer 1

$1 + 2 + 3 + ..... + 100 = \frac{100 \times 101}{2} \\ = 5050 \\ \\ 7 + 4 + 21 + ..... + 700 = \\ 7 \times (1 + 2 + 3 + ..... + 100) = \\ 7 \times 5050 = 35350$