Q3 of 104 Page 444

Find the 7th and nth terms of the GP 0.4, 0.8, 1.6….

Given GP is 0.4, 0.8, 1.6….


The given GP is of the form, a, ar, ar2, ar3….


Where r is the common ratio.


First term in the given GP, a1 = a = 0.4


Second term in GP, a2 = 0.8


Now, the common ratio,



Now, nth term of GP is, an = arn – 1


So, the 7th term in the GP,


a7 = ar6


= 0.4 x 26


= 25.6


nth term in the GP,


an = arn – 1


= (0.4)(2) n – 1


= (0.2)2n


Hence, 7th term = 25.6 and nth term = (0.2)2n


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