The students in three batches of a course are in the ratio 2 : 3 : 5. If 20 students are increased in each batch, the ratio changes to 4 : 5 : 7. What was the total number of students in the three batches combined before the increase?

If all the girls in school B and school C participated in the function, find the ratio between the number of boys in school B and school C who participated in the function.

Which of the following examples represents an inverse proportional relationship (reverse movement)?