If 20 men can build a water fountain 56 metres long in 7 days, what length of a similar water fountain can be built by 35 men in 3 days? Options
A) 40 m  B) 42 m  C) 47 m  D) 49 m  E) 50 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 7: 3 : : 56 : x   Therefore (20 x 7 x x)=(35 x 3 x 56)   x=(35 x 3 x 56)/140=42   Hence, the required length is 42 m.   Answer : 42 m
<result>B</result>
If 20 men can build a water fountain 56 metres long in 7 days, what length of a similar water fountain can be built by 35 men in 3 days?