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Aiswarya Ram Gupta Grade: 12
        

n AMs are  inserted between 1 & 51. If ratio between 4th & 7th AMs is 3:5, then n equals??

6 years ago

Answers : (2)

vikas askiitian expert
510 Points
										

first term of this AP series is 1 , so a =1


now nth term(Tn) = a+(n-1)d                            (d is common ration of this series)


 4th term of AMs means 5th term of AP ...so T5 = a+4d = 1+ 4d


 7th term of AMs means 8th term of AP ...so T8 = a+7d = 1+7d


ratio is given = 3/5


 1+4d/1+7d = 3/5


5+20d = 3+21d


  d = 2


now ,let there are n terms  in this Ap then


 a + (n-1) = 51


 1 + (n-1)2 = 51        or


 n = 26


approve my ans if u like it


 


 

6 years ago
Aiswarya Ram Gupta
35 Points
										

thnx

6 years ago
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