Answer:
40.49
Step-by-step explanation:
First term: a n term: aₙ common ratio: r sum of first n term: sₙ
a + (ar) = a(r+1) = 36
a * ar² = 9 * ar .... divide ar both side
ar = 9 ... 2nd term
a + (ar) = a + 9 = 36
a = 27 ... first term
r = 9/27 = 1/3
sₙ = a (1 - rⁿ) / (1-r) n=8
s₈ = 27 * (1 - 1/3⁸) / (1 - 1/3)
= 27 * (1 - 1/6561) / 2/3
= 27 * (6560/6561) / 2/3
= 27 * 3280/2187
= 3280/81
= 40.49
