**Topic**

In the short run competition at school level, class 10B had 15 students registered for the 100m content test, and 10 students registered for the 200m content test. Knowing that class 10B has 40 students and 19 students have not registered for any content test. How many students in class 10B registered for both content?

**Detailed explanation**

Number of students registered to participate in at least one content is 40 – 19 = 21 (students).

Number of students registered to participate in both content is: 15 + 10 – 21 = 4 (students).

So there are 4 students registered to participate in both content.