Pipe A fills a tank of capacity 750 liters at the rate of 40 liters a minute. Another pipe B fills the same tank at the rate of 30 liters a minute. A pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute. If pipe A is kept open for a minute and then closed and pipe B is open for a minute and then closed and then pipe C is open for a minute and then closed and the cycle is repeated, when will the tank be full?  Select the correct option.
A) 45 minutes	B) 14 minutes	C) 39 minutes	D) 40 minutes 20 seconds	E) None of these
In one cycle they fill 40+30-20= 
<gadget id="calculator">40+30-20</gadget>
<output>50</output>
50 liters   750= 50*n =&gt; n = 15   here n = number of cycles.   total time = 15*3= 
<gadget id="calculator">15*3</gadget>
<output>45</output>
45 as in one cycle there are 3 minutes.   thus 45 minutes   45 minutesNSWER:45 minutes
<result>A</result>
Pipe A fills a tank of capacity 750 liters at the rate of 40 liters a minute. Another pipe B fills the same tank at the rate of 30 liters a minute. A pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute. If pipe A is kept open for a minute and then closed and pipe B is open for a minute and then closed and then pipe C is open for a minute and then closed and the cycle is repeated, when will the tank be full?