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Question: Sum of infinite number of terms of a G.P. is 20 and sum of their square is 100. The common ratio of ...

Sum of infinite number of terms of a G.P. is 20 and sum of their square is 100. The common ratio of the G.P. is-

A

1/5

B

8/5

C

3/5

D

5

Answer

3/5

Explanation

Solution

If sum of  terms of G.P. is = x

sum of  term of their square is = y

then common ratio is

= x2−yx2+y\frac { x ^ { 2 } - y } { x ^ { 2 } + y }= (20)2−100(20)2+100\frac { ( 20 ) ^ { 2 } - 100 } { ( 20 ) ^ { 2 } + 100 }= 300500\frac { 300 } { 500 }= 35\frac { 3 } { 5 }