SOLUTION: Given the following, solve for the unknown quantity. 1. Given:S4=120,r=3;find a1. 2. Given:S5=496,r=1/2;find a1. sn=sum of the number r=common ratio a1=first term

Algebra ->  Sequences-and-series -> SOLUTION: Given the following, solve for the unknown quantity. 1. Given:S4=120,r=3;find a1. 2. Given:S5=496,r=1/2;find a1. sn=sum of the number r=common ratio a1=first term      Log On


   

Question 1185483: Given the following, solve for the unknown quantity.

1. Given:S4=120,r=3;find a1.
2. Given:S5=496,r=1/2;find a1.
sn=sum of the number
r=common ratio
a1=first term
Answer by ikleyn(52817) About Me  (Show Source):
You can put this solution on YOUR website!
.

        Part 1 

a + 3a + 9a + 27a = 120


40a = 120


a = 120/40 = 3.    ANSWER


        Part 2 

a + a%2F2 + a%2F4 + a%2F8 + a%2F16 = 496


%2816a%29%2F16 + %288a%29%2F16 + %284a%29%2F16 + %282a%29%2F16 + a%2F16 = 496


%2831a%29%2F16 = 496


a = %28496%2A16%29%2F31 = 256.    ANSWER

Solved.