9 engines consume 24 metric tonnes of coal, when each is working 8 hours day. How much coal is required for 8 engines, each running 13 hours a day, if 3 engines of former type consume as much as 4 engines of latter type?	Choose the most appropriate option:
A) 20 metric tonnes	B) 22 metric tonnes	C) 24 metric tonnes	D) 26 metric tonnes	E) None of these
Explanation :   Let required amount of coal be x metric tonnes   More engines, more amount of coal (direct proportion)   If 3 engines of first type consume 1 unit, then 1 engine will consume 1/3 unit which is its the rate of consumption.   If 4 engines of second type consume 1 unit, then 1 engine will consume 1/4 unit which is its the rate of consumption   More rate of consumption, more amount of coal (direct proportion)   More hours, more amount of coal(direct proportion)   ⇒ 9 × (1/3) × 8 × x = 8 × (1/4) × 13 × 24   ⇒ 3 × 8 × x = 8 × 6 × 13   ⇒ 3 × x = 6 × 13   ⇒ x = 2 × 13 = 26. Answer : Option 26 metric tonnes
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9 engines consume 24 metric tonnes of coal, when each is working 8 hours day. How much coal is required for 8 engines, each running 13 hours a day, if 3 engines of former type consume as much as 4 engines of latter type?