document.write( "Question 784618: A group of men decided to do a job in 4days. but since 20 men dropped out everyday, the job completed at the end of the 7th day. How many men were there at the beginning? \n" ); document.write( "
Algebra.Com's Answer #477173 by htmentor(1343)\"\" \"About 
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Let n = the number of men at the beginning
\n" ); document.write( "The rate of work = 1 job/4 days/n men
\n" ); document.write( "Assuming the first group of 20 did not drop out until the end of the first day, n men worked the first day.
\n" ); document.write( "So after the 1st day, 1/4 of the job was complete
\n" ); document.write( "On the 2nd day n-20 men completed (1/4n)*(n-20) of the job
\n" ); document.write( "On the 3rd day n-40 men completed (1/4n)*(n-40) of the job, and so on.
\n" ); document.write( "After 7 days, the entire job is complete, so we can sum up all the fractions of the job done on each day and set them equal to 1:
\n" ); document.write( "1 = 1/4 + (n-20)/4n + (n-40)/4n + (n-60)/4n + (n-80)/4n + (n-100)/4n + (n-120)/4n
\n" ); document.write( "3/4 = (6n - 420)/4n
\n" ); document.write( "Solve for n:
\n" ); document.write( "12n = 24n - 1680
\n" ); document.write( "12n = 1680
\n" ); document.write( "n = 140
\n" ); document.write( "So there were 140 men at beginning
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