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A milkman makes 20% profit by selling milk mixed with water at $ 9 per litre. If the cost price of 1 litre pure milk is $ 10, then the ratio of milk and water in the said mixture is
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- 3 : 1
- 4 : 1
- 3 : 2
- 4 : 3
Correct Option: A
Let Milk : Water = K : 1
∴ S.P. = (K + 1) × 9
Cost price of 1 litre pure milk is $ 10 i.e.
C.P. = 10K
Gain = S.P. - C.P. = 9K + 9 - 10k = 9 – K
| Gain % = | × 100 | 10K |
| ⇒ | × 100 = 20 | 10K |
⇒ 90 – 10K = 20K
⇒ 30K = 90
⇒ K = 3
∴ Ratio = 3 : 1
