Eight litres are drawn off from a vessel full of water and substituted by pure milk. Again eight litres of the mixture are drawn off and substituted by pure milk. If the vessel now contains water and milk in the ratio 9:40, find the capacity of the vessel. Choose one:
A) 21 liters B) 22 liters C) 20 liters D) 14 liters E) 28 liters
Lets start with option:   Vessel capacity be 20litre:   8litre water removed and milk added: W=12litre, M=8litre   8litre mixture removed, (removed proportionately) : W= 12-4.8= 
<gadget id="calculator">12-4.8</gadget>
<output>7.2</output>
7.2litre, M= 8-3.2= 
<gadget id="calculator">8-3.2</gadget>
<output>4.8</output>
4.8 litre   8litre milk added ; W=7.2 litre, M=12.8 litre   Ratio will be 72/128 = 18/32 = 9/16   As we can see that milk is less so we have to select the ratio even less than 20,   Vessel capcity be 14 litre   8litre water removed and milk added: W=6 litre, M=8 litre   8litre mixture removed, (removed proportionately) : W= 6-3.4= 
<gadget id="calculator">6-3.4</gadget>
<output>2.6</output>
2.6 litre, M= 8-4.6= 
<gadget id="calculator">8-4.6</gadget>
<output>3.4</output>
3.4 litre   8litre milk added ; W=2.6 litre, M=11.4 litre   Ratio will be 26/114 = 8.66/38 (approx) very close to 9/40   So correct option is 14 liters
<result>D</result>
Eight litres are drawn off from a vessel full of water and substituted by pure milk. Again eight litres of the mixture are drawn off and substituted by pure milk. If the vessel now contains water and milk in the ratio 9:40, find the capacity of the vessel.