Question

l 5 + 6 + 7 + 8 +... + 19' का योगफल बराबर है। (1) 150 (3) 180 (2) 170 (4) 190

11th - 12th Class

Maths

Solution

4.0 (1 ratings)

n(n+1) 1. (3) 1+ 2+3 +.... +n=- 2 ... 5+ 6+ 7+ ... + 19 = (1 + 2 + 3 + ... + 19) - (1 + 2 + 3 + 4) 19(19+1) - 10 = 180