If 9 engines consume 24 metric tonnes of coal, when each is working 8 hoursa day, how much coal will be required for 8 engines, each running 13 hours a day, it is being given that 3 engines of former type consume as much as 4 engines of latter type?
Choices:
A) 23  B) 25  C) 26  D) 28  E) 30
Explanation :   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 proportion)   Number of engines 9: 8   Working hours 8 : 13 } :: 24 : x   Rate of consumption (1/3):(1/4)   ( 9 * 8 * (1/3) * x) = (8 * 13 * (1/4) * 24 ) &lt;=&gt; 24x = 624 &lt;=&gt; x = 26.   Answer : 26
<result>C</result>
If 9 engines consume 24 metric tonnes of coal, when each is working 8 hoursa day, how much coal will be required for 8 engines, each running 13 hours a day, it is being given that 3 engines of former type consume as much as 4 engines of latter type?