Answer:
195.25
Step-by-step explanation:
Consider geometric series S(n) where initial term is a
So S(n)=a+ar^1+...ar^n
Factor out a
S(n)=a(1+r+r^2...+r^n)
Multiply by r
S(n)r=a(r+r^2+r^3...+r^n+r^n+1)
Subtract S(n) from S(n)r
Note that only 1 and rn^1 remain.
S(n)r-S(n)=a(r^n+1 -1)
Factor out S(n)
S(n)(r-1)=a(r^n+1 -1)
The formula now shows S(n)=a(r^n+1 -1)/(r-1)
Now use the formula for the problem
Janes weight = x
Twelve pounds less than twice janes weight is 270 pounds
12 less than 2x is 270
2x -12 = 270 (add 12 to each side)
2x = 270 + 12
2x = 282 (divide 2 from each side)
x = 282/2
x = 141
The answer is 141 pounds
