Two pipes A and B can fill a tank in 10 hrs and 40 hrs respectively. If both the pipes are opened simultaneously, how much time will be taken to fill the tank?	Answers:
A) 8 hours	B) 6 hours	C) 4 hours	D) 2 hours	E) None of these
Explanation :   Pipe 8 hours can fill 1⁄10 of the tank in 1 hr   Pipe B can fill 1⁄40 of the tank in 1 hr   Pipe 8 hours and B together can fill 1⁄10 + 1⁄40 = 1⁄8 of the tank in 1 hr   i.e., Pipe 8 hours and B together can fill the tank in 8 hours .8 hoursnswer : Option 8 hours
<result>A</result>
Two pipes A and B can fill a tank in 10 hrs and 40 hrs respectively. If both the pipes are opened simultaneously, how much time will be taken to fill the tank?