Tap 'A' can fill the tank completely in 6 hrs while tap 'B' can empty it by 12 hrs. By mistake, the person forgot to close the tap 'B', As a result, both the taps, remained open. After 2 hrs, the person realized the mistake and immediately closed the tap 'B'. In how much time now onwards, would the tank be full?	Choose the correct answer.
A) 2 hours	B) 4 hours	C) 5 hours	D) 1 hour	E) None of these
Explanation :   Tap A can fill the tank completely in 6 hours   =&gt; In 1 hour, Tap A can fill 1⁄6 of the tank   Tap B can empty the tank completely in 12 hours   =&gt; In 1 hour, Tap B can empty 1⁄12 of the tank   i.e., In one hour, Tank A and B together can effectively fill 1⁄6 - 1⁄12 = 1⁄12 of the tank   =&gt; In 2 hours, Tank A and B can effectively fill 1⁄12 × 2= 1⁄6 of the tank.   Time taken to fill the remaining 1−(1/6) = 5/6 of the tank = (5/6)/(1/6)= 
<gadget id="calculator">(5/6)/(1/6)</gadget>
<output>5</output>
5 hours. Answer : Option 5 hours
<result>C</result>
Tap 'A' can fill the tank completely in 6 hrs while tap 'B' can empty it by 12 hrs. By mistake, the person forgot to close the tap 'B', As a result, both the taps, remained open. After 2 hrs, the person realized the mistake and immediately closed the tap 'B'. In how much time now onwards, would the tank be full?