Q5 of 8 Page 180

Three numbers are in G.P whose sum is 70. If the extreme is each multiplied by 4 and the mean by 5 they will be in A.P. Find the numbers.


Their sum = 70


a(r2 + r + 1) = 70 r …….(i)




5ar = 2ar2 + 2a


2r2 – 5r + 2 = 0


2r2 – 4r – r + 2 = 0


⇒ r = 2 or 0.5


From r = 2 and 0.5 putting value in eq(i)


⇒ a = 20


So terms are 10 20 40


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