Question

If the sum of 'n' terms of two A.P. are in the ratio (7n + 1) : (4n +27) then their 11^th terms are in the ratio-

• A. 3 : 4
• B. 4 : 3
• C. 78 : 61
• D. 152 : 119

Answer 1

Answer: (B)

4 : 3

Answer 2

$\frac{S_{n}}{S_{n}^{'}}$=$\frac{7n + 1}{4n + 27}$

replace n ® 2k –1

n ® 2 × 11 –1 = 21

$\frac{T_{11}}{T_{11}^{'}}$=$\frac{21 \times 7 + 1}{21 \times 4 + 27}$= $\frac{148}{111}$= $\frac{4}{3}$