Page 43 - ICSE Math 7

3 Decimals

Key Concepts

• Decimal Fractions • Fundamental Operations on Decimals
• Conversion of Fractions into Decimals • Terminating and Non-Terminating Decimals
• Conversion of Decimals into Fractions • Approximation
• Comparison of Decimals

The word ‘decimal’ is derived from the Latin word decem which means ten. Sometimes, numbers
do not appear as whole numbers or factions. Instead, they appear in the form of decimal numbers as

.
28.53. The . in the decimal number is called the decimal point. Decimal point ( ) separates the
‘ ’
integral part on the left from the decimal part on the right. The numbers expressed in decimal form
are also known as decimals.
We have learnt about decimal numbers in our previous classes. In this chapter, we will learn about
decimal fractions, fundamental operations on decimals, terminating and non-terminating decimals,
approximation and significant figures.

Decimal Fractions
Fractions having denominator 10 or a higher powers of 10 are called decimal fractions. For example,
3 , 14 and 29 are decimal fractions. The number of digits in the decimal part of a number is equal
10 100 1000
to the number of decimal places in it. For example, 7.456 has three decimal places.
We can extend our Indian place value chart by moving right to the ones place to include decimal
fractions.
Let’s have a look at the following place value chart to understand decimals.
Integral part Decimal part

Thousands Hundreds Tens Ones Decimal point Tenths Hundredths Thousandths
1 1 1
1000 100 10 1 .
10 100 1000

3 4 2 1 . 3 2
Let’s learn how to write and read numbers using decimal notation.

The first place to the right of the decimal point is known as the first decimal place and it is occupied
by tenths. Similarly, the second and third decimal places are occupied by hundredths and thousandths
respectively, and so on. Let’s learn how to write and read numbers using decimal notation.
3
(i) is written as 0.03 and is read as zero point zero three.
100 Maths Info
245
(ii) is written as 0.245 and is read as zero point two four five. Since proper fractions do not
1,000 have a digit on the left of the
9 decimal point, a zero is written on
(iii) 72 100 is written as 72.09 and is read as seventy-two point zero the left side of the decimal point.
nine.

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