1.

If the ratio between the sums of n terms of two arithmetic progressions is (7n + 1) : (4n + 27), find the ratio of their 11th terms.

Answer»

Given: Ratio of sum of nth terms of 2 AP’s

To Find: Ratio of their 11th terms

Let us consider 2 AP series AP1 and AP2.

Putting n = 1, 2, 3… we get

AP1 as 8, 15 22… and AP2 as 31, 35, 39….

So, a1 = 8, d1 = 7 and a2 = 31, d2 = 4

For AP1

S6 = 8 + (11 - 1)7 = 87

For AP2

S6 = 31 + (11 - 1)4 = 81

Required ratio = 87/81 = 29/27



Discussion

No Comment Found