[" 2.In a class there are "30" students.On the New year day,every student posts a greeting card to all "],[" his / her classmates.Find the total number of greeting cards posted by them."]

In a class there are certain number of students. On the new year day every student posts a greeting card to all of his classmates. If the total number of greeting cards posted by them is 870. Then find the number of students.

In a class, there are 45 students. On a new year eve, every student sends one greeting card to each of the other students. How many greeting cards were exchanged in all?

In a class there are 30 students. If each student plays a game of chess with each other student, then find the total number of games played by them.

On the occasion if Deepawali festival, each student in a class sends greeting cards to other. If there are 20 students in the class, find the total number of greeting cards exchanged by the students?

On the occasion if Deepawali festival, each student in a class sends greeting cards to other. If there are 20 students in the class, find the total number of greeting cards exchanged by the students?

In a class there are 50 students. If each student plays a chess game with each other student, then find the total number of games played by them

On the occasion of Dipawali festival each student of a class sends greeting cards to the others . If there are 20 students in the class , then the total number of greeting cards exchanged by the students is

On the occasion of Deepawali festival, each student of a class sends greeting cards to the others. If there are 20 students in the class, then the total number of greeting cards exchanged by the students is

On a new year day every student of a class sends a card to every other student.The postman delivers 600 cards.The number of students in the class are

On the event of new year each student of class XI sends cards to his classmates. If there are 40 students in the class number of cards exchanged during the process is