It has been decided that the flag of a newly formed forum will be in the form of three blocks, each coloured differently. If there are six colours on the whole to choose from, how many designs are possible ?

Where are B-cells and T-cells formed ? How do they differ from each other?

A number lock on a suitcase has 3 wheels each labeled with ten digits from 0 to 9. If the opening of the lock is a particular sequence of three digits with no repeats, how many such sequences will be possible?

What is the number of ways of choosing 4 cards from a pack of 52 playing cards ? In how many of these : cards are of the same colour ?

In a monthly test, the teacher decides that there will be three questions. one from each of Exercises 5, 6 and 7 of the text book. If there are 12 questions in Exercise 5, 18 in Exercise 6 and 9 in Exercise 7, in how many ways can the three questions be selected ?

The digits, from 0 to 9, are written on slips of paper and placed in a box. Three of the Slips of paper are drawn and placed in order. How many different outcomes are possible ?

The students in a class are seated according to the marks in the previous examination. Once it so happens that four of these students get equal marks and therefore the same rank. To decide their seating arrangement, the teacher wants to write down all possible arrangements, one in each of separate bits of paper, in order to choose one of these by lots. How many bits of paper are required ?

Given 5 flags of different colours, how many different signals can be generated if each signal requires the use of 2 flags, one below the other?

How many necklace of 12 beads, each can be made from 18 beads of various colours?

How many different 4-digit numbers can he formed from the digits 2, 3, 4 and 6 if each digit is used only once in a number ? Further, how many of these numbers : end in a 4 ?