3 persons can build a wall in 4 days, then 4 persons can build it in
More the no. of persons, lesser the days to build. So, it is an inverse proportion.
Let the required duration be x days.
⇒ 3 × 4 = 4 × x
⇒ x = 
= 3 days
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3 persons can build a wall in 4 days, then 4 persons can build it in
More the no. of persons, lesser the days to build. So, it is an inverse proportion.
Let the required duration be x days.
⇒ 3 × 4 = 4 × x
⇒ x = = 3 days