To determine how many females there would be in the class if there are 15 males, we can use the initial ratio of males to females, which is 3 males for every 5 females.
Let's set up the ratio table:
| Males | Females | |-------|---------| | 3 | 5 | | 6 | 10 | (doubling the first row: 2 * 3 = 6 and 2 * 5 = 10) | 9 | 15 | (tripling the first row: 3 * 3 = 9 and 3 * 5 = 15) | 12 | 20 | (4 times the first row: 4 * 3 = 12 and 4 * 5 = 20) | 15 | 25 | (5 times the first row: 5 * 3 = 15 and 5 * 5 = 25)
From this ratio table, we can see that if there are 15 males, there would be 25 females in the class.
So the answer is: There would be 25 females in the class if there are 15 males.