Question
If the ratio of the sum of first three terms and the sum of first six terms of a G.P. be 125 : 152, then the common ratio r is ___.
Answer: Option A
:
A
Given that a+ar+ar2a+ar+ar2+ar3+ar4+ar5=125152.
⇒1+r+r21+r+r2+r3+r4+r5=125152i.e.,1+r+r2(1+r+r2)+r3(1+r+r2)=125152⇒11+r3=125152⇒r3=152125−1=27125⇒r=35
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:
A
Given that a+ar+ar2a+ar+ar2+ar3+ar4+ar5=125152.
⇒1+r+r21+r+r2+r3+r4+r5=125152i.e.,1+r+r2(1+r+r2)+r3(1+r+r2)=125152⇒11+r3=125152⇒r3=152125−1=27125⇒r=35
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