Question

Without adding find the sum:
(I) 1+3+5+7+9+11
(ii) 1+3+5+7+9+11+13 ​

Answer 1

Answer:

1) 36

2)49

Hint => first add those numbers which will make 0 in ones place.

Jai Shree Ram

Answer 2

Answer:

i) here, a=1, d=3-1=2, n=6 and l=11

so, 1+3+5+7+9+11 = n/2(a+l)

= 6/2(1+11) = 3×12 =36.

ii) here, a=1, d=3-1=2, n=7 and l=13

so, 1+3+5+7+9+11+13 = n/2(a+l)

= 7/2(1+13) = 7/2(14) = 7×7 = 49.