Twelve pipes of equal capacity can fill a tank in four days. If the tank has to be filled in 3 days, the number of extra pipes needed is:	Answers:
A) 4  B) 7  C) 16  D) 28  E) 30
Explanation :   3 : 4 :: 12 : x   or 3x =4 * 12   or x = 4*12/3= 
<gadget id="calculator">4*12/3</gadget>
<output>16</output>
16   Extra pumps needed= (16 - 12)= 
<gadget id="calculator">(16 - 12)</gadget>
<output>4</output>
4.   4nswer : 4
<result>A</result>
Twelve pipes of equal capacity can fill a tank in four days. If the tank has to be filled in 3 days, the number of extra pipes needed is: