. Mr.P and Mr.Q can build a wall in 10 days; Mr.Q & Mr.R can take 14 days to build the same wall; and Mr.P and Mr.R can do it in 8 days. Who among them will take more time when they work alone?  Choose the correct choice from the following choices:
A) 8.8  B) 8.7  C) 1.3  D) 8.6  E) 8.5
Answer: b   Explanation:   Let the total work be 280 units.   Now P and Q capacity per day = 280/10= 
<gadget id="calculator">280/10</gadget>
<output>28</output>
28 units.   Q and R capacity per day=280/14= 
<gadget id="calculator">280/14</gadget>
<output>20</output>
20 units   P and R capacity per day= 280/8 = 25 units.   Adding all the three,   2(P + Q + R) = 73 ⇒ P + Q + R = 36.5 units.   We are asked to find who will take maximum time. So the capacity is minimum. R capacity is minimum as (P + Q + R) - (P + R) = 36.5 - 28 = 8.5.   Answer:8.5
<result>E</result>
. Mr.P and Mr.Q can build a wall in 10 days; Mr.Q & Mr.R can take 14 days to build the same wall; and Mr.P and Mr.R can do it in 8 days. Who among them will take more time when they work alone?