Question 684598
if 3 people can build a wall in 25 minutes, how long will it take for 5 people to build the same wall
<pre>
First way:

The LCM of 3 people and 5 people is 15 people.  15 people can build a wall in
1/5 the the time that only 3 people can or 1/5th of 25 minutes, or 5 minutes.
5 people will take 3 times as long as 15 people, and 3 times 5 minutes is 15
minutes.
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Second way:

Use the worker-time-job formula, which is:

{{{(W[1]T[1])/J[1]}}}{{{""=""}}}{{{(W[2]T[2])/J[2]}}}

where

W<sub>1</sub> = the number of workers in the first situation.
T<sub>1</sub> = the number of time units (minutes in this case) in the first situation.
J<sub>1</sub> = the number of jobs in the first situation.

W<sub>2</sub> = the number of workers in the second situation.
T<sub>2</sub> = the number of time units (minutes in this case) in the second situation.
J<sub>2</sub> = the number of jobs in the second situation.

W<sub>1</sub> = 15             W<sub>2</sub> = 5     
T<sub>1</sub> = 25             T<sub>2</sub> = the unknown quantity 
J<sub>1</sub> =  1             J<sub>2</sub> = 1

{{{(W[1]T[1])/J[1]}}}{{{""=""}}}{{{(W[2]T[2])/J[2]}}}

{{{(3*25)/1}}}{{{""=""}}}{{{(5*T[2])/1}}}

{{{75}}}{{{""=""}}}{{{5T[2]}}}

{{{75/5}}}{{{""=""}}}{{{T[2]}}}

{{{15}}}{{{""=""}}}{{{T[2]}}}

Answer: 15 minutes.
  
Edwin</pre>