Find three numbers in G.P. whose sum is 65 and whose product is 3375.

Let the three numbers be .


According to the question


…(1)


…(2)


From 2 we get,


a3 = 3375


a = 15.


From 1 we get,



a + ar + ar2 = 65r …(3)


Substituting a = 15 in 3 we get


15 + 15r + 15r2 = 65r


15r2 – 50r + 15 = 0…(4)


Dividing (4) by 5 we get


3r2 – 10r + 3 = 0


3r2 – 9r – r + 3 = 0


3r(r – 3) – 1(r – 3) = 0


r = 3 or r = 1/3


Now the equation will be



5,15,45 or 45,15,5.


The three numbers are 5,15,45.


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