Question

i) Find the sum of n terms of an arithmetic progression, whose 7 th term is 30 and 13 th term is 54​

Answer 1

Answer:

n(2n+4)

Step-by-step explanation:

nth term formula of AP is

t=a+(n-1)d

So, 30=a+(7-1)d

30=a+6d----(i)

54=a+(13-1)d

54=a+12d------(ii)

Solving (i) & (ii), we get

a=6 & d=4

Sum of nth term of an AP series is

S=n/2[2a+(n-1)d]

Putting values of a & d,we get

S=n(2n+4)