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Question
In a G.P., the fourth term is 48 and the eighth term is 768. Find the tenth term.
Solution
Given, t4 = 48, t8 = 768
tn = arn–1
∴ t4 = ar3
∴ ar3 = 48 ...(i)
and ar7 = 768 ...(ii)
Equation (ii) ÷ equation (i), we get
`"ar"^7/"ar"^3 = 768/48`
∴ r4 = 16
∴ r = 2
Substituting r = 2 in (i), we get
a.(23) = 48
∴ a = 6
∴ t10 = ar9
∴ t10 = ar9
= 6(29)
= 3072.
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