If 18 persons can build a wall 140 m long in 42 days, the number of days that 30 persons will take to complete a similar wall 100 m long, is? Choose the correct choice from the following options
A) 28
B) 18
C) 24
D) 21
E) 16
Explanation :   (Length 140:100) : (Persons 30:18) :: 42 : x140 x 30 x X = 100 x 18 x 42 or X = 18   Answer : 18
<result>B</result>
If 18 persons can build a wall 140 m long in 42 days, the number of days that 30 persons will take to complete a similar wall 100 m long, is?