Q9 of 97 Page 185

The sums of n terms of two arithmetic progressions are in the ratio 5n + 4 : 9n + 6. Find the ratio of their 18th terms.

Let a1, a2, and d1, d2 be the first terms and the common difference of the first and second arithmetic progression respectively.


Given,



⇒


Putting n = 35 in the above equation


⇒


⇒



∴


Thus, the ratio of 18th term of both the A.P.s is 179: 321


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