Total Questions: 80
Discount 10% Selling price = 150 x (100-10)/100
=150*90\100=Rs. 135
No of Books = 3510\135= 26
Total age of 5 students 16x5=80
Total age of 40 students =525+80=605
Average age of 40 students 605\40=15.125 years
This situation is called summer solstice or North solstice.