Question 763594: The average attendance of the workers in a factory in July, August and September is 180, and in August, September and October is 185. if there are 170 workers present in October, then find out the number of workers present in July?
Answer by ramkikk66(644)   (Show Source):
You can put this solution on YOUR website! Average of July - Sep (let's represent the months as J, A and S) is 180.
So J + A + S = 180*3 = 540 ----- eqn (1)
Average of Aug - October (let's represent the months as A, S and O) is 185.
So A + S + O = 185*3 = 555 ----- eqn (2)
170 were present in October, so O = 170.
Substituting for O in eqn(2), A + S + 170 = 555, so A + S = 555 - 170 = 385 --- (3)
Now, substituting for (A+S) in eqn (1)
J + (A+S) = J + 385 = 540, so J = 540 - 385 = 155.
No. of workers in July = 
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