In a student's reunion meeting in a school, 16 students show up. Each shakes hands with each other exactly once. Determine the total number of handshakes.

Two mirrors are kept at 60^@ to each other and a body is placed at middle .The total number of images formed is

If there are 12 persons in a party, and if each two of them shake hands with each other, how many handshakes happen ?

Eighteen guests have to be Seated, half on each side of a long table. Four particular guests desire to sit on one particular side and three others on the other side. Determine the number of ways in which the Seating arrangements can be made.

In an examination hall, there are four rows of chairs. Each row has 8 chairs one behind the other. There are two classes sitting for the examination with 16 students in each class. It is desired that in each row, all students belong to the same class and that no two adjacent rows are allotted to the same class. In how many ways can these 32 students be seated?

In a class of 25 students, 12 have taken Mathematics. 8 have taken Mathematics but not Biology. Find the number of students who have taken both Mathematics and Biology and the number of those who have taken Biology but not Mathematics. Each student has taken either Mathematics or Biology or both.

Out of 1800 students in a school,750 opted basketball,800 opted cricket and remaining opted table tennis.If a student can opt only one game,find the ratio of: Number of students who opted basketball to the total number of students.