NCERT Book Class 8 Maths Playing with Numbers

16.1 Introduction
You have studied various types of numbers such as natural numbers, whole numbers, integers and rational numbers. You have also studied a number of interesting properties about them. In Class VI, we explored finding factors and multiples and the relationships among them.
In this chapter, we will explore numbers in more detail. These ideas help in justifying tests of divisibility.

16.2 Numbers in General Form

Let us take the number 52 and write it as

                                             52 = 50 + 2 = 10 × 5 + 2

Similarly, the number 37 can be written as

                                             37 = 10 × 3 + 7

In general, any two digit number ab made of digits a and b can be written as

                                            ab = 10 × a + b = 10a + b

What about ba? ba = 10 × b + a = 10b + a

Let us now take number 351. This is a three digit number. It can also be written as

                                             351 = 300 + 50 + 1 = 100 × 3 + 10 × 5 + 1 × 1

Similarly                                 497 = 100 × 4 + 10 × 9 + 1 × 7

In general, a 3-digit number abc made up of digits a, b and c is written as

                                              abc = 100 × a + 10 × b + 1 × c

                                                    = 100a + 10b + c

In the same way,

                                                        cab = 100c + 10a + b

                                                        bca = 100b + 10c + a                  and so on.

Please refer to attached file for NCERT Class 8 Maths Playing with Numbers