Question

15 students join a summer course every day 3 students are on duty after school to clean the classroom after the pause it was found that every pair of students have been on duty together exactly once how many days did the course last for​

Answer 1

Step-by-step explanation:

35 days.

No of combinations of 3 students from 15 students = 15!/(12!*3!) = 15*14*13/6= 35*13but here each pair has worked with other 13 persons once.

As per given condition,

each pair worked together only once.

so possible combinations = no of days of course = 35*13/13= 35

Hope this will help you buddy...

Have a nice day ahead...

Answer 2

Answer:

35

Step-by-step explanation:

Step-by-step explanation:

35 days.

No of combinations of 3 students from 15 students = 15!/(12!*3!) = 15*14*13/6= 35*13but here each pair has worked with other 13 persons once.

As per given condition,

each pair worked together only once.

so possible combinations = no of days of course = 35*13/13= 35

Hope this will help you , mark as brainliest