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The sum of the first and third terms of a geometric progression is 40 while the fourth and sixth term are in the ratio 1:4 . Find the common ratio and fifth term

 Jul 26, 2020
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4th term is   1 out of (4+1)  = 1/5      sixth term is   4/5

1/5 x r x r = 4/5

r^2 = 4    r =2

 

1st and third terms     x   +   x * r * r  = 40

                                    x + 4x = 40

                                     x = 8 = first term

 

5th term   8 r^4 = 8 * 16 = 128              

 Jul 27, 2020

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