Theory:

A number is a mathematical object which is used to count and measure.
Let's recall the classification of numbers that we learned in the previous grades.
 
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Important!
  • Every natural number is a whole number, integer and rational.
  • Every whole number is an integer and rational.
  • Every integer is a rational number.
Here come the pictorial forms of the classification of numbers:
 
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By the definition of a subset of a set, the following result is obvious.
 
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