Question

Find the sum of the first 24 terms of list of nos. whose nth term is an = 3n + 1?

Thanks!

Answer 1

an = 3n + 1

a1 = 3×1 + 1 = 4

a24 = 3 × 24 + 1 = 73

Sn = n /2(a + l)

S24 = 24/2 ( 4 + 73)

S24 = 12 × 77

S24 = 924


Thanks

Answer 2

Final Answer : 924

We know,
a(n) = 3n+1
a(1) = 3*1+1 = 4
a(24) = 3*24 + 1 = 72+1 = 73


Now,
S(n) =n/2 ( a(1) + a(n))
=> S(24) = 24/2 ( 4+73)
=> S(24) =12 * 77 = 924


Hence,
Sum of 24 terms is 924