A sum of Rs. 1550 was lent partly at 5% and partly at 8% p.a. simple interest. The total interest received after 3 years was Rs. 300. The ratio of the money lent at 5% to that lent at 8% is:
Choose the correct choice.
A) 16 : 15 B) 15 : 16 C) 15 : 8 D) 8 : 15 E) 8 : 17

Rationale: explanation : let the partial amount at 5 % be x and the partial amount at 8 % be ( 1550 - x ) interest on x at 5 % for 3 years + interest on ( 1550 - x ) at 8 % for 3 years = 300 x × 5 × 3 / 100 + ( 1550 - x ) × 8 × 3 / 100 = 300 x × 5 / 100 + ( 1550 - x ) × 8 / 100 = 100 5 x + 8 ( 1550 − x ) = 10000 5 x + 12400 − 8 x = 10000 3 x = 2400 x = 800 required ratio = x : ( 1550 - x ) = 800 : ( 1550 - 800 ) = 800 : 750 = 16 : 15 answer : option a
Answer: A