MathematicsClass 7Fractions and Decimals
Operations on Decimals
Performing addition, subtraction, multiplication, and division with decimal numbers.
Class 7 · MathematicsCBSE & ICSE SOF IMO
Definition
Operations on decimals include addition, subtraction, multiplication, and division. For addition and subtraction, numbers must be aligned by their decimal points. For multiplication, numbers are multiplied as whole numbers, and the decimal point is placed in the product by counting total decimal places.
Key formula
Align decimal points for addition and subtraction; count total decimal places for multiplication
Worked examples
1
Add 3.45 and 1.2: 3.45 + 1.20 = 4.65
2
Multiply 0.5 and 0.4: 5 times 4 = 20, with two decimal places gives 0.20 or 0.2
3
Subtract 5.8 from 10.2: 10.2 - 5.8 = 4.4
Common mistakes
- • Aligning the rightmost digits instead of the decimal points during addition and subtraction.
- • Incorrectly placing the decimal point in the final product during multiplication by ignoring the number of decimal places.