Class 7 Maths
Rational Numbers
Ex. 9.1 Q.1
List five rational numbers between:
(i) -1 and 0 (ii) -2 and -1 (iii) and
(iv)
and
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1
Introduction:
If a and b are two integers, then each of a + b, a - b and a x b is also an
integer.
However, it is not necessary that a b or b a is also an integer.
For example:
Consider two integers 8 and 5.
Clearly:
(i) 8 + 5 = 13 is an integer. (ii) 8 - 5 = 3 is an integer 5 - 8 = -3 is also an
integer.
Here, and are fractions and are said to form the system of rational numbers.
RATIONAL NUMBERS
∙If p and q are two co-prime integers and q 0, then the number is called a
rational number.
∙p and q are co-primes, p and q do not have any common factor other than
1.
Example:
(i) is a rational number as 3 and 7 both are integers and 7 0.
(ii) is a rational number as -15 is an integer, 19 is an integer and 19 0.
Rational Numbers in standard form:
A rational number is in standard form, if n is positive and m and n have only 1
as their common factor.
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Class 7 Mathematics ICSE | Rational Number | Notes
(i) Rational number is in standard form as 4 is positive and both 3 and 4 have
only 1 as their common factor.
(ii)Rational number is not in standard form as 24 is positive but 15 and 24 have
1 and 3 as their common factors.
Remember:
1. Every integer is a rational number but the converse is not true
(i) 5= is a rational number as 5 and 1 as integers and 1 0.
(ii) -8 = is a rational number as -8 and 1 as integers and 1 0.
(iii) Every natural number is an integer and so a rational number.
(iv) Every whole number is also an integer and so a rational number.
2. Each of 0 = , , …. etc. is a rational number.
3. In a rational number in the form of a fraction , p is called the numerator and
q is called the denominator.
In numerator = 7 and denominator = 11.
4. Positive rational number: A rational number is said to be positive, if its
numerator and denominator both are either positive or negative.
Each of the following rational numbers is a positive rational number:
etc.
5. Negative rational number: A rational number is said to be negative, if its
numerator and denominator are with opposite signs, i.e., if the numerator is
positive and the denominator is negative or if the numerator is negative and
the denominator is positive.
etc.
6. (i) Every positive integer (i.e., every natural number) is a positive rational
number.
e.g., natural numbers 5 = is a positive rational number.
(ii) Every negative integer is a negative rational number.
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Class 7 Mathematics ICSE | Rational Number | Notes
e.g., -5 = is a negative rational number.
Zero (0) is a rational number but it is neither positive nor negative.
REPRESENTATION OF RATIONAL NUMBERS ON NUMBER LINE
1. Draw a straight line. Mark a point O on this line and name it 0 (zero).
2. On the right side of O, mark points A, B, C, D, E, .... on the line drawn such
that the distance between consecutive points is the same.
i.e., OA =AB= BC= CD= ...........
3. In the same way, on the same line mark points A', B', C', D', etc. on the left
side of O such that:
OA' = A'B' = B'C' = ...........
On the whole, we must have;
......... B'C' = A'B' = OA' = OA = AB = BC = CD = .........
The points A, B, C, D, E, ........., which are on the right side of zero (0), represent
positive integers 1, 2, 3, 4, 5, ......... and the points A', B', C', D', E', ........., which
are on the left side of zero, represent negative integers -1, -2, -3, -4, -5, ......... .
Example:
Represent rational numbers on the same number line.
Answer:
Consider C'B' = B' A' = A'O = OA = AB = BC = one unit length Clearly, A
represents 1, B represents 2 and C represents 3.
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Class 7 Mathematics ICSE | Rational Number | Notes
In the same way, A' represents -1, B' represents = -2 and C' represents -3. Since
denominator of each given rational number is 2, mark middle points of each of
OA, AB, BC and OA', A'B', B'C' to divide each of OA, AB, BC and OA', A'B', B'C'
into two equal parts. Now the given points are marked on this number line.
Comparing Rational Number
1. Every positive rational number is greater than 0 (zero) and is greater than
every negative number:
e.g., 8 > 0, 8 > - 5, 8 > -93, 8 > -1235, etc.
2. Every negative rational number is less than 0 (zero) and is less than every
positive number:
e.g., -8 < 0, -8 < 5, -8 < 93, -8 < 123, etc.
3. Zero (0) is greater than every negative number and is smaller than every
positive number:
e.g., 0 > -5, 0 > , 0 < 5, 0 < etc. Example:
Compare
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Ex. 9.1 Q.2
Write four more rational numbers in each of the following patterns:
(i) (ii)
(iii) (iv)
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Ex. 9.1 Q.3
Give four rational numbers equivalent to:
(i) (ii)
(iii)
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Ex. 9.1 Q.4
Draw the number line and represent the following rational numbers on it:
(i) (ii)
(iii)
(iv)
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Ex. 9.1 Q.5
The points P, Q, R, S, T, U, A and B on the number line are such that, TR = RS = SU and AP = PQ = QB. Name the rational numbers represented by P, Q, R and S.
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Ex. 9.1 Q.6
Which of the following pairs represent the same rational numbers:
(i) (ii)
(iii)
(iv)
(v)
(vi) (vii)
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Ex. 9.1 Q.7
Rewrite the following rational numbers in the simplest form:
(i) (ii)
(iii)
(iv)
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Ex. 9.1 Q.8
Fill in the boxes with the correct symbol out of <, > and =:
(i) (ii)
(iii)
(iv)
(v) (vi)
(vii)
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Ex. 9.1 Q.9
Which is greater in each of the following:
(i) (ii)
(iii)
(iv)
(v)
,
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Ex. 9.1 Q.10
Write the following rational numbers in ascending order:
(i) (ii)
(iii)
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Ex. 9.2 Q.11
Find the sum:
(i) (ii)
(iii)
(iv)
(v) (vi)
(vii) -2
+ 4
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Ex. 9.2 Q.2
Find:
(i) (ii)
(iii)
(iv) (v) -2
– 6
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Ex. 9.2 Q.3
Find the product:
(i) (ii)
(iii)
(iv)
(v) (vi)
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Ex. 9.2 Q.4
Find the value of:
(i) (ii)
(iii)
(iv)
(v) (vi)
(vii)
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