Adding And Subtracting Decimals - Definition with Examples

Adding and Subtracting Decimals

Decimal number

• A decimal number is a fraction whose denominator is a power of 10. For example, the fraction ⁴⁄₁₀  can be written in decimal form as 0.4, where:

• The dot is called the decimal point.

• The number to the right of the decimal point denotes the numerator of the fraction, that is, the fractional part.

• The number to the left of the decimal point denotes the whole number part of the fraction.

• For example, 4 ³⁄₁₀  is expressed as 4.3, where 4 is the whole number part and 0.3 is the fractional part. 

• The decimal point separates the whole number part from the fractional part. 

Decimals in real life

We deal with decimal addition and subtraction in everyday life while dealing with:

• Money

• Measurements (Length, Mass, Capacity)

• Temperature

Decimals can be added or subtracted in the same way as we add or subtract whole numbers.

Steps to add or subtract Decimals:

• Convert decimals to like decimals. (Decimals that have the same number of digits after the decimal point are like decimals).

• Write the decimals one below the other as per the places of the digits.

• Add or subtract starting from the rightmost digit and moving towards the leftmost digit.

• Place the decimal point under the decimal point in the answer. 

Example: Add 23.45; 13.101 and 345.5 

1.  Convert to like decimals: The highest decimal place is 3, so we add zeros in other numbers and get 3 decimal places in them too.

    13.101

    23.45 = 23.450

2.  Line up the decimals:

 

3.  Add:

4.  Place decimal in answer:

Example: Kylie had 25 m of ribbon. She uses 8 m and 13 cm to decorate a skirt. How much ribbon is remaining with Kylie?

Solution:

Length of ribbon Kylie had = 25 m = 25.00         

Length of ribbon used by Kylie = 8 m 13 cm = 8.13

The remaining length of ribbon = 25.00 – 8.13

                                             = 16.87