If 9 engines consume 24 metric tonnes of coal, when each is working 8 hoursday, bow much coal will be required for 8 engines, each running 13hours a day, it being given that 3 engines of former type consume as much as 4 engines of latter type? Choose the correct choice.
A) 22 B) 24 C) 26 D) 28 E) None of them
Let 3 engines of former type consume 1 unit in 1 hour.   Then, 4 engines of latter type consume 1 unit in 1 hour.   Therefore 1 engine of former type consumes(1/3) unit in 1 hour.   1 engine of latter type consumes(1/4) unit in 1 hour.   Let the required consumption of coal be x units.   Less engines, Less coal consumed (direct proportion)   More working hours, More coal consumed (direct proportion)   Less rate of consumption, Less coal consumed(direct prportion)   Number of engines 9: 8   Working hours	8 : 13 } :: 24 : x   Rate of consumption (1/3):(1/4)   [ 9 x 8 x (1/3) x x) = (8 x 13 x (1/4) x 24 ) = 24x = 624 = x = 26.   Hence, the required consumption of coal = 26 metric tonnes.   Answer is 26.
<result>C</result>
If 9 engines consume 24 metric tonnes of coal, when each is working 8 hoursday, bow much coal will be required for 8 engines, each running 13hours a day, it being given that 3 engines of former type consume as much as 4 engines of latter type?