Problem 647

Sir SagarMarch 18, 2015March 18, 20150

Find S15 for 1 + 1.5 + 2.25 + 3.375 + …

Solution:-

Sn = $\frac{ a1(1 - r^{n})}{(1 - r) }$ , Where a1 = first term , r = common ratio and n = finding term.

a1 = 1 , r = 1.5 , n = 15

S15 = $\frac{ 1(1 - 1.5^{15})}{(1-1.5)}$

S15 = 873.79

So the value of S15 873.79

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