A mixture of 70 litres of milk and water contains 10% water. How many litres of water should be added to the mixture so that the mixture contains 12 1/2% water?
Correct answer: A. 2
- A. 2
- B. 8
- C. 4
- D. 5
- E. None of these
Explanation
The original water is 10% of 70 litres, or 7 litres. If x litres of water are added, (7 + x)/(70 + x) = 12.5% = 1/8; hence 8(7 + x) = 70 + x, giving 56 + 8x = 70 + x and x = 2 litres. The likely wrong answer is 4 litres, which results from applying 12.5% to the original 70 litres instead of the enlarged mixture.
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