Class 7 Maths Fractions and Decimals Addition and Subtraction of Decimal Numbers

Addition and Subtraction of Decimal Numbers

Addition of Decimal numbers:

The rules for addition of numbers with Decimals are:

  • Numbers are written under each other. The decimal points lie under each other, in the same vertical line.
  • Addition is done column wise.
  • Addition is started from the right hand side and then we move to the left hand side.

 

Subtraction of Decimal numbers:

The rules for subtraction are:

  • The smaller number is written under the bigger number.
  • The numbers are written in such a way that the decimals are in the same vertical line.
  • Subtraction is started from the right hand side.

 

Problem: Which is greater?  5 or 0.05

Place Value of digits is compared from the left till we find a greater place value.

 

Place Value – 0.50

Relation between place value

 

Place value -0.05

0*1 = 0

 

=

0*1 = 0

5*1/10 = 0.5

 

0*1/10 = 0

 

Since 0.5 is greater than 0, there is no need of further comparing the place value of digits. 0.5 is greater than 0.05.

099 or 0.19

Place value is compared:

 

Place Value – 0.099

Relation between place value

 

Place value -0.19

0*1 = 0

 

=

0*1 = 0

0*1/10 = 0

 

1*1/10 = 0.1

 

Since 0.1 is greater than 0, there is no need of further comparing the place value of digits. 0.19 is greater than 0.099.

 

Problem: Express as rupees using decimals: 7 paise

 

1 Rupee = 100 paise

100 paise = 1 Rupee

1 paise =1/100 Rupee

7 paise = 7/100 Rupee

7 paise = 0.07 Rupees

Thus, the answer is 0.07 rupees.

 

7 rupees 7 paise

1 Rupee = 100 paise

100 paise = 1 Rupee

1 paise =1/100 Rupee

7 paise = 7/100 Rupee

7 paise = 0.07 Rupees

 

Thus, the answer is 7 rupees + 7 paise = 7 rupees + 0.07 rupees

= 7.07 rupees.

 

Problem: Write the place value of 2 in the following decimal numbers: 56

2 is located at the one’s place.

Place value of 2 is 2*1 = 2.

(ii) 21.37

2 is located at the one’s place.

Place value of 2 is 2*10 = 20

 

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