If there are 12 persons in a party and each of them shake hands with all others, what is the total number of handshakes?

In 90 gram of water: What will be the total number of atoms?

Suppose that in a party there are 15 persons If each two of the 15 persons shake hands, with each other, how many handshakes happen in the party

What will be the ascending order of the total number of atoms.

In 90 gram of water: What will be the total number of electrons in this sample?

Three letters are dictated to three persons and an envelope is addressed to each of them the letters are inserted into the envelopes at random so that each envelop contains exactly one letter . find the probability that at least one letter is in its proper envelope.

Three letters are dictated to three persons and an envelope is addressed to each of them, the letters, are inserted' into the envelopes at random so that each envelope contains exactly one letter. Find the probability that at least one letter is in its proper envelope.

It was found at a certain dinner meeting that after every member had shaken hand with every other members, 45 handshakes were interchanged. How many members were present at the meeting?

All the 8 edges of a pyramid are of equal length. If the length of one edge is '10 cm', a) What is the total length of all edges? b) What is the total total surface area of the pyramid?