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NCERT Solutions for Class 9 Math Chapter 1.1 NUMBER SYSTEM ALL SOLUTION

CLASS :- 9, EX :- 1.1



1. Is zero a rational number? Can you write it in the form pq, where p and q are integers and q ≠ 0?

solution :

   We know that, a number is said to be rational if it can be written in the form pq , where p and q are integers and q ≠ 0.

    Zero can be written in the form  0,01,02,03,04,0-1,0-2,0-3,0-4,...........

   Hence, zero is a rational number.

2.    Find six rational numbers between 3 and 4.

solution :

   There are infinite rational numbers between 3 and 4.

   As we have to find 6 rational numbers between 3 and 4.

   we will multiply both the numbers, 3 and 4, with 6+1 = 7.

   Example : 3×(77)=217 and 4×(77)=287.

   The numbers in between 217 and 287 will be rational and will fall between 3 and 4.

   Hence, 227,237,247,257,267,277are the 6 rational numbers between 3 and 4.

3.    Find five rational numbers between 35 and 45.

solution :

   There are infinite rational numbers between 35 and 45.

   To find out 5 rational numbers between 35 and 45.

   we will multiply both the numbers 35 and  45

   with 1010 (or any number greater than 5)

   Example : (35)×(1010)=3050 and (45)×(1010)=4050.

   The numbers in between 3050 and 4050 will be rational and will fall between 35 and 45.

    Hence, 3150,3250,3350,3450,3550 are the 5 rational numbers between 35 and 45.

4.    State whether the following statements are true or false. Give reasons for your answers.
      (i) Every natural number is a whole number.
      (ii) Every integer is a whole number.
      (iii) Every rational number is a whole number.

solution :

   (i) Every natural number is a whole number.

   TRUE

   Natural numbers : Numbers starting from 1 to infinity

   Example : Natural numbers= 1, 2, 3, 4, 5, 6, 7, ...............,∞.

   Whole numbers : Numbers starting from 0 to infinity

   Example : Whole numbers= 0, 1, 2, 3, 4, 5, 6, 7,....................., ∞.

   Or, we can say that whole numbers have all the elements of natural numbers and zero.

   Hence, Every natural number is a whole number.

   (ii) Every integer is a whole number.,

   FALSE

   Integers : Integers are set of numbers that contain positive,negative and 0.

   Example : integers are -∞, .........-6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, ........, ∞.

   Whole numbers : Numbers starting from 0 to infinity.

   Example : Whole numbers are 0, 1, 2, 3, 4, 5, .............,∞.

   Or, we can say that every integers are not whole numbers.

   Hance, Every integer is not a whole number.

   (iii) Every rational number is a whole number.

   FALSE

   Rational numbers : All numbers in the form pq, where p and q are integers and q ≠ 0.

   Example : Rational numbers are 0,-15,27,0-9,-17,...............,∞.

   Whole numbers : Numbers starting from 0 to infinity.

   Example : Whole numbers and 0, 1, 2, 3, 4, 5, 6, 7, .............., ∞.

   Or, we can say that every Rational numbers not Whole numbers.

   Hence, All rational numbers are not whole numbers.



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