It's a milky day
Algebra
Level
3
A dishonest milkman has one bucket of milk of 80% purity.He has another bucket of milk of 60% purity.How much milk from first bucket should he mix to supply 20 liters of milk of 75% purity ?
The answer is 15.
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1 solution
Intuitively, one can observe that 75 lies three-fourths of the way from 60 to 80, therefore, three-fourths of the final quantity should be 80% milk and the remaining 60% milk.
We can use simultaneous equations to solve this problem.
In the first bucket, there are 0 . 8 l of pure milk in 1 l of milk. In the second bucket, there are 0 . 6 l of pure milk in 1 l of milk.
Certain volumes of milk from each of the two buckets are mixed in order to obtain 2 0 l milk of 7 5 % purity.
Therefore , x + y = 2 0 0 . 8 x + 0 . 6 y = 0 . 7 5 × 2 0
Solving which gives x as 15, which is the answer.