If 15 girls can sweep a room in 3 hours. Assume that all girls work at the same rate. How many girls can sweep the same room in 5 hours?

If 15 girls can sweep a room in 3 hours, then the total work done by the girls is 15 girls * 3 hours = 45 girl-hours.

To find out how many girls can sweep the same room in 5 hours, we divide the total work by the number of hours:

45 girl-hours / 5 hours = 9 girls

Therefore, 9 girls can sweep the same room in 5 hours.