Question

1+3+5+7+9+11+13 Solve this without adding

Answer 1

it is in A.P

so sum = 7/2*(1+13)

answer is 49

Answer 2

We can solve it using AP
There are 7 terms(n=7) and (a)first term is 1and last term(l) is13.
So, by using the formula
Sn=n[a+l]/2
S7=7[1+13]/2=7*14/2=49
Thus the sum of the given numbers is 49..

Hope it helps you...