It takes 7 people 12 hours to complete a job. If they worked at the same rate,
how many people would it take to complete the job in 16 hours.

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



where

W1 = the number of workers in the first situation.
T1 = the number of time units (days in this case) in the first situation.
J1 = the number of jobs in the first situation.

W2 = the number of workers in the second situation.
T2 = the number of time units (days in this case) in the second situation.
J2 = the number of jobs in the second situation.

W1 = 7            W2 = the unknown quantity     
T1 = 12            T2 = 16 
J1 = 1             J2 = 1

[There was only 1 job, so the number of jobs in both situations is 1.







      84 = 16W2
      
Divide both sides by 8

       = W2

       = W2

The answer would be  workers. But since it's not nice to
cut workers in fourths :), we have to use 6 workers. and get it
done in less than 16 hours.

Edwin