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?	Select the correct option:
A) Rs. 1000  B) Rs. 1200  C) Rs. 1400  D) Rs. 1600  E) Rs. 2500
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=pnr100   ⇒   1600   =   7000   ×   5   ×   r   100   ⇒   r   =   1600   ×   100   7000   ×   5   =   160   35   =   32   7   %   ⇒1600=7000×5×r100⇒r=1600×1007000×5=16035=327%   By rule of alligation,   Rate of interest % from part1	Rate of interest % from part2   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   =&gt; Part1 : part2   =   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 (part1 amount)   =   7000   ×   2   7   =Rs. 2000   Rs. 1600)
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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?