In 40 litres of a mixture, the ratio of milk to water is 7:1. In order to make the ratio of milk to water as 3:1, the quantity of water that should be added to the mixture will be?
Choose the correct option:
A) rs . 1000
B) rs . 1200
C) rs . 1400
D) rs . 1600
E) rs . 2500

Rationale: explanation : total simple interest received , i = rs . 1600 principal , p = 7000 period , n = 5 years rate of interest , r = ? simple interest , i = p n r 100 i = pnr 100 ⇒ 1600 = 7000 × 5 × r 100 ⇒ r = 1600 × 100 7000 × 5 = 160 35 = 32 7 % ⇒ 1600 = 7000 × 5 × r 100 ⇒ r = 1600 × 1007000 × 5 = 16035 = 327 % by rule of alligation , rate of interest % from part 1 rate of interest % from part 2 6 4 net rate of interest % 32 7 327 32 7 − 4 = 4 7 327 − 4 = 47 6 − 32 7 = 10 7 6 − 327 = 107 = > part 1 : part 2 = 4 7 : 10 7 = 4 : 10 = 2 : 5 = 47 : 107 = 4 : 10 = 2 : 5 given that total amount is rs . 7000 . therefore , the amount lent at 6 % per annum ( part 1 amount ) = 7000 × 2 7 = rs . 2000 d )
Answer: D