If 20 men can build a well 56 meters long in 6 days,What length of a similar wall can be built by 35 men in 3 days?

Explanation:
Let the required length be x meters

More men, More length built (Direct proportion)

Less days, Less length built (Direct Proportion)

Men20:35Days6 : 3}⋮⋮ 56 😡

=> (20 x 6 x X)=(35 x 3 x 56)

=> x = 49

Hence, the required length is 49 m.