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Find the 6th and the nth terms of the list of numbers 32,34,38,...\dfrac{3}{2}, \dfrac{3}{4}, \dfrac{3}{8}, …

AP GP

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Answer

The given list of numbers

32,34,38,...\dfrac{3}{2}, \dfrac{3}{4}, \dfrac{3}{8}, … is a G.P. with first term a = 32\dfrac{3}{2} and common ratio = r = 12.\dfrac{1}{2}.

By formula, an = arn - 1

a6=32(12)61=32(12)5=32×132=364.an=32(12)n1=32×2n×21=32n.a6 = \dfrac{3}{2}\Big(\dfrac{1}{2}\Big)^{6 - 1} = \dfrac{3}{2}\Big(\dfrac{1}{2}\Big)^5 = \dfrac{3}{2} \times \dfrac{1}{32} = \dfrac{3}{64}. \\[1em] an = \dfrac{3}{2}\Big(\dfrac{1}{2}\Big)^{n - 1} = \dfrac{3}{2 \times 2^n \times 2^{-1}} = \dfrac{3}{2^n}.

Hence, the 6th term is 364 and nth term is 32n.\dfrac{3}{64} \text{ and nth term is } \dfrac{3}{2^n}.

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