Question

find the sum of all natural numbers from 15 to 30​

Answer 1

Answer:

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15

which equals

(1+15) + (2+14) + (3+13) + (4+12) + (5+11) + (6+10) + (7+9) + 8

which equals

16 + 16 + 16 + 16 + 16 + 16 + 16 + 8

which equals

7 x 16 + 8

which equals

112 + 8

which equals

120.

That’s it!