SOLUTION: A group of students volunteered to finish a construction work in 25 days. 1Q of the students did not come and the work could be finished in 35 days. The original number of students

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Question 995668: A group of students volunteered to finish a construction work in 25 days. 1Q of the students did not come and the work could be finished in 35 days. The original number of students in the group were?































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Answer by josgarithmetic(39621) About Me  (Show Source):
You can put this solution on YOUR website!
The description leaves three unknown variables.

EXPECTED:
p students to do 1 job in 25 days.
Let r be the rate for 1 student.
pr%2A25=1, the work rate equation for p students.

FEWER STUDENTS:
Now, p-Q students came to do the job and time required was 35 days.
%28p-Q%29r%2A35=1.

The system of these two equations can be solved for p. See the THREE unknown variables, p, r, and Q. You might assume that either r or Q would be a constant.

pr%2A25=%28p-Q%29r%2A35
25rp=pr%2A35-Qr%2A35
25rp-35rp=-35Qr
Multiply by -5;
7rp-5rp=7Qr
p%287r-5r%29=7Qr
p=%287Qr%29%2F%282r%29
highlight%28p=7Q%2F2%29, original number of students expected.