Answer:
Sum is about 4.9423
Step-by-step explanation:
We want the sum: 1+.8+.8^2+.8^3+...+.8^19
Common ratio = r = 0.8
First term : a_1 = 1
20 terms here.
nth term : a_n = a_1 * r^(n - 1)
a_n = 1 * (0.8)^(n - 1)
Sum of first 20 terms = S
S = a_1 * ( ( r^20) - 1) / ( r - 1)
S = 1 * ( (0.8^20) - 1 ) / (0.8 - 1)
S = [(0.8^20) - 1 ] / (-0.2)
S = -0.98847078495393153024 / (-0.2)
S = 4.94235
