Mathematics
The fourth term of a Geometric Progression (G.P.) is 16 and its seventh term is 128. Find its:
(a) common ratio
(b) first term
G.P.
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Answer
(a) We know that,
an = arn - 1
Given,
a4 = ar3 = 16 ….(1)
a7 = ar6 = 128 …..(2)
Dividing equation (2) by equation (1), we get :
Hence, common ratio = 2.
(b) The first term,
Substituting r = 2 in equation (1), we get :
⇒ a(2)3 = 16
⇒ a(8) = 16
⇒ a =
⇒ a = 2.
Hence, first term = 2.
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