Decimal numbers use 10 digits, which are combined to make numbers of any size. The position of the digit determines what it means in any number. For example, the 2 in the number 200 is ten times the size of the 2 in the number 20. Each position of a number gives a value ten times higher than the position to its right. So 9867 means 7 units, plus 6 x 10, plus 8 x 10 x 10, plus 9 x 10 x 10 x 10. As decimal numbers are based on the number 10, we say that this is a base -10 number system.

We have learnt that the decimals are an extension of our number system. We also know that decimals can be considered as fractions whose denominators are 10, 100, 1000, etc. The numbers expressed in the decimal form are called decimal numbers or decimals.

For example: 5.1, 4.09, 13.83, etc.

A decimal has two parts:

(a) Whole number part

(b) Decimal part

These parts are separated by a dot (.) called the decimal point.

  • The digits lying to the left of the decimal point form the whole number part. The places begin with ones, then tens, then hundreds, then thousands and so on.
  • The decimal point together with the digits lying on the right of decimal point form the decimal part. The places begin with tenths, then hundredths, then thousandths and so on…


(i) In the decimal number 211.35; the whole number part is 211 and the decimal part is .35

(ii) In the decimal number 57.031; the whole number part is 57 and the decimal part is .031

(iii) In the decimal number 197.73; the whole number part is 197 and the decimal part is .73

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