The sum of the first 3 terms in a geometric series with common ratio 3 is 52. What are the values of t1 and t6?

1 Answer
Nov 15, 2016

t1=4
t6=972

Explanation:

You start by finding a in the formula sn=a(1rn)1r, since we know the sum, the common ratio (r) and the number of terms.

52=a(133)13

52(2)=a(127)

104=26a

a=10426

a=4

Hence, the first term is 4. We can find the 6th term using the formula for the nth term of a geometric sequence, tn=a×rn1.

t6=4×361

t6=972

Hopefully this helps!