Answer:
19
Step-by-step explanation:
This is a geometric series.
15, 3, (3/5), ...
common ratio r = 3/15 = (1/5)
a_1 = 15
Formula for nth term: a_n = a_1 * r^(n-1)
a_n = 15 *(1/5)^(n - 1)
We want the sum of the first 7 terms.
S = a_1 * ( r^n - 1) / (r - 1)
here let n = 7
S = 15 * ( (1/5)^7 - 1 ) / ( (1/5) - 1)
S = 15 * ( (1/5)^7 - 1) / (-4/5)
S = 15 * (5/-4) * ( (1/5)^7 - 1)
S = ( -75/4 )* (-0.9999872)
S = - (-18.74976) = 18.749...
The sum is about 19