| A mixture of 40 L of milk and water contains 10% of water. How much water must be added to make the water 20% in the new mixture? [SSC (10+2) 2010, (CGL) 2003] |
A) 10 L
B) 7 L
C) 5 L
D) 3 L
Correct Answer: C
Solution :
| In a mixture of 40 L, |
| Water \[=\frac{40\times 10}{100}=4\,\,L\] |
| According to the question, |
| If the quantity of water mixed be x L, then |
| \[(4+x)=(40+x)\times 20\]% |
| \[\Rightarrow \] \[4+x=\frac{(40+x)20}{100}\] |
| \[\Rightarrow \]\[5\,\,(4+x)=40+x\]\[\Rightarrow \]\[20+5x=40+x\] |
| \[\Rightarrow \] \[4x=40-20=20\] |
| \[\therefore \] \[x=\frac{20}{4}=5\,\,\text{L}\] |
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