A and B together can plough a field in 10 hours but by himself A requires 15 hours. How long would B take to plough the same field? Pick:  A) 10 hours  B) 20 hours  C) 30 hours  D) 40 hours  E) 50 hours
If A and B together can do a piece of work in x days and A alone can do the same work in y days,   then B alone can do the same work in x y/ y – x days.   Therefore, the No. of hours required by B = 10 × 15/ 15 – 10 = 150/5= 
<gadget id="calculator">150/5</gadget>
<output>30</output>
30 hours.   Answer : 30 hours
<result>C</result>
A and B together can plough a field in 10 hours but by himself A requires 15 hours. How long would B take to plough the same field?