In one class in the school, number of abscent students is of number of students who were present. When teacher sent one student to bring chalk, number of abscent students was of number of students who were present. How many students are in that class?
Problem 1370
Official solution
1. Let be the number of students who were present initially.
2. Let be the number of students who were absent initially.
From the problem, we know:
3. When the teacher sent one student to bring chalk, the number of present students becomes , and the number of absent students remains .
4. At this point, the number of absent students is of the number of present students:
5. We now have two equations:
6. Substitute from the first equation into the second equation:
7. To eliminate the fractions, multiply both sides by 30 (the least common multiple of 6 and 5):
8. Simplify and solve for :
9. Substitute back into the first equation to find :
10. The total number of students in the class is the sum of the present and absent students:
The final answer is