640 ml of a mixture contains milk and water in ratio 6:2. How much of the water is to be added to get a new mixture containing half milk and half water?

• A. 360 ml
• B. 320 ml
• C. 330 ml
• D. 310 ml

Answer: (B)

Here total parts of milk and water in the solution is 6+2 = 8 parts. 1part = 640/8 = 80   old mixture contains 6parts of milk and 2 parts of water(6:2).   To get new mixture containing half milk and half water, add 4parts of water to the old mixture then 6:(2+4) to make the ratio same. i.e, 4 x 80 = 320 ml.