Question

Evaluate...

Answer 1

evaluate what?

Answer 2

\[\sum_{n=3}^{12}20(0.5)^{n-1}\]

Answer 3

A. 9.99
B. 19.95
C. 29.98
D. 39.96

Answer 4

I have no idea what to do :/

Answer 5

The summation is summing up a geometric series starting with 3 and ending at 12.

The series you are summing up is 20(.5)^(n-1).

Use the formula for the sum of ageometric series, starting with 3 and ending with 12.

Answer 6

I'm still so lost

Answer 7

@hartnn

Answer 8

@gorv

Answer 9

it is a geomatric series

Answer 10

\[20\sum_{2}^{12} (0.5)^n-1\]

Answer 11

\[20\sum_{2}^{12} (0.5)^(n-1)\]

Answer 12

20(0.5^(2-1)+0.5^(3-1)+.............+0.5^(12-1))
20(0.5^1 + 0.5^2 + 0.5 ^3 + .................+0.5^11)
it is a g.p inside the brackket
with a=0.5 and r=0.5

Answer 13

use the summition formula of g.p

Answer 14

@P.nut1996

Answer 15

GP=a(1-r^n)/(1-r)

where n is number of terms =11
total sum=10*GP

Answer 16

sorry
total sum=20*GP