Question

If the ratio of the sum of first n terms of two A.P is (7n+1):(4n+27), find the ratio of their 10th terms

Answer 1

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Answer 2

hi

here is your answer

Now.

[n/2(2a1+(n−1)d1)]/[n/2(2a2+(n−1)d2)]=7n+1/4n+27

Cancelling common terms on the left hand side,

(2a1+(n−1)d1)/(2a2+(n−1)d2)=7n+1/4n+27

Taking 2 common on both sides,

∴(a1+(n−1)2d1)(a2+(n−1)2d2)=7n+1/2/4n+27/2

∴(a1+(n−1)2d1)/(a2+(n−1)2d2)=7n+1/4n+27...(equation1)

Now we have to find the ratio of 10th term,

(n−1)/2=9

∴n−1=18

∴n=19

Putting n=19 in equation number 1 we get,

∴(a1+9d1)/(a2+9d2)=7∗19+1/4∗19+27

∴(a1+9d1)/(a2+9d2)=134/103

hope it helps

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