Adding And Subtracting Decimals - Definition with Examples

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Adding and Subtracting Decimals

Decimal number

• A decimal number is a fraction whose denominator is a power of 10. For example, the fraction 410  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, 4 310  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

345.5 = 345.500

2.  Line up the decimals:  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 Fun Facts The word “decimal” originated in the early 17th century from the Latin word “decimus” which means “tenth”. We use decimals when we want precise and accurate answers.

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