SOLUTION: The second period College Algebra class of 33 students could do n problems in x hours. If 3 students were absent, how long would it take to do 100 problems???

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Question 964114: The second period College Algebra class of 33 students could do n problems in x hours. If 3 students were absent, how long would it take to do 100 problems???
Answer by Edwin McCravy(20064) About Me  (Show Source):
You can put this solution on YOUR website!
The second period College Algebra class of 33 students could do n problems in x
hours. If 3 students were absent, how long would it take to do 100 problems???
33 students can do n problems in x hours.
Therefore, 1 student would take 33 times as long, So

1 student can do n problems in 33x hours.

Therefore, 1 student can do 1 problem in that time divided by n.  So:

1 student can do 1 problem in 33x%2Fn hours.  

Therefore 1 student can do 100 problems in 100 times as long.  So:

1 students can do 100 problems in 3300x%2Fn hours.  So with 3
students absent: 

33-3=30 students could do them in that time divided by 30.  So

Solution: 3300x%2Fn%22%F7%2230%22%22=%22%223300x%2Fn%22%D7%221%2F30%22%22=%22%22%283300x%29%2F%2830n%29%22%22=%22%22110x%2Fn

30 students can do 100 problems in 110x%2Fn hours. 

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Another way is to use the worker-time-job formula, which is:

%28W%5B1%5DT%5B1%5D%29%2FJ%5B1%5D%22%22=%22%22%28W%5B2%5DT%5B2%5D%29%2FJ%5B2%5D

where

W1 = the number of workers in the first situation.
T1 = the number of time units (hours 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 (hours in this case) in the second situation.
J2 = the number of jobs in the second situation.

W1 = 33             W2 = 30     
T1 =  x             T2 = the unknown quantity
J1 =  n             J2 = 100

%28W%5B1%5DT%5B1%5D%29%2FJ%5B1%5D%22%22=%22%22%28W%5B2%5DT%5B2%5D%29%2FJ%5B2%5D

%2833%2Ax%29%2Fn%22%22=%22%22%2830%2AT%5B2%5D%29%2F100

Cross-multiply

30nT2 = 3300x

Divide both sides by 30n

T2 = 3300x%2F%2830n%29 = 110x%2Fn

Answer: 30 students can do 100 problems in 110x%2Fn hours.
  
Edwin