If 20 men can build a water fountain 56 metres long in 21 days, what length of a similar water fountain can be built by 35 men in 3 days? Choose one.
A) 10 m	B) 14 m	C) 17 m	D) 19 m	E) 20 m
Explanation :   Let the required length be x metres   More men, More length built (Direct Proportion)   Less days, Less length built (Direct Proportion)   Men 20: 35   Days 21: 3 : : 56 : x   Therefore (20 x 21 x x)=(35 x 3 x 56)   x=(35 x 3 x 56)/420=14   Hence, the required length is 14 m.   Answer : 14 m
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If 20 men can build a water fountain 56 metres long in 21 days, what length of a similar water fountain can be built by 35 men in 3 days?