NCERT Solutions for Class 7 Maths Chapter 9 - Rational Numbers

By observing the figure, we can say that,

The distance between A and B = 1 unit

And it is divided into 3 equal parts = AP = PQ = QB = 1/3

P = 2 + (1/3)

= (6 + 1)/ 3

= 7/3

Q = 2 + (2/3)

= (6 + 2)/ 3

= 8/3

Similarly,

The distance between U and T = 1 unit

And it is divided into 3 equal parts = TR = RS = SU = 1/3

R = – 1 – (1/3)

= (- 3 – 1)/ 3

= – 4/3

S = – 1 – (2/3)

= – 3 – 2)/ 3

= – 5/3

 

(i) In the above question, we can observe that the numerator and denominator are multiples of 3 and 5.

= (-3 × 1)/ (5 × 1), (-3 × 2)/ (5 × 2), (-3 × 3)/ (5 × 3), (-3 × 4)/ (5 × 4)

Then, the next four rational numbers in this pattern are,

= (-3 × 5)/ (5 × 5), (-3 × 6)/ (5 × 6), (-3 × 7)/ (5 × 7), (-3 × 8)/ (5 × 8)

= -15/25, -18/30, -21/35, -24/40 ….

(ii) In the above question, we can observe that the numerator and denominator are multiples of 1 and 4.

= (-1 × 1)/ (4 × 1), (-1 × 2)/ (4 × 2), (-1 × 3)/ (1 × 3)

Then, the next four rational numbers in this pattern are,

= (-1 × 4)/ (4 × 4), (-1 × 5)/ (4 × 5), (-1 × 6)/ (4 × 6), (-1 × 7)/ (4 × 7)

= -4/16, -5/20, -6/24, -7/28 ….

(iii) In the above question, we can observe that the numerator and denominator are multiples of 1 and 6.

= (-1 × 1)/ (6 × 1), (1 × 2)/ (-6 × 2), (1 × 3)/ (-6 × 3), (1 × 4)/ (-6 × 4)

Then, the next four rational numbers in this pattern are,

= (1 × 5)/ (-6 × 5), (1 × 6)/ (-6 × 6), (1 × 7)/ (-6 × 7), (1 × 8)/ (-6 × 8)

= 5/-30, 6/-36, 7/-42, 8/-48 ….

(iv) In the above question, we can observe that the numerator and denominator are the multiples of 2 and 3.

= (-2 × 1)/ (3 × 1), (2 × 1)/ (-3 × 1), (2 × 2)/ (-3 × 2), (2 × 3)/ (-3 × 3)

Then, the next four rational numbers in this pattern are,

= (2 × 4)/ (-3 × 4), (2 × 5)/ (-3 × 5), (2 × 6)/ (-3 × 6), (2 × 7)/ (-3 × 7)

= 8/-12, 10/-15, 12/-18, 14/-21 ….

 

(i) The five rational numbers between -1 and 0 are,

-1< (-2/3) < (-3/4) < (-4/5) < (-5/6) < (-6/7) < 0

(ii) The five rational numbers between -2 and -1 are,

-2 < (-8/7) < (-9/8) < (-10/9) < (-11/10) < (-12/11) < -1

(iii) The five rational numbers between -4/5 and -2/3 are,

-4/5 < (-13/12) < (-14/13) < (-15/14) < (-16/15) < (-17/16) < -2/3

(iv) The five rational numbers between -1/2 and 2/3 are,

-1/2 < (-1/6) < (0) < (1/3) < (1/2) < (20/36) < 2/3

 

(i) The four rational numbers equivalent to -2/7 are,

= (-2 × 2)/ (7 × 2), (-2 × 3)/ (7 × 3), (-2 × 4)/ (7 × 4), (-2 × 5)/ (7× 5)

= -4/14, -6/21, -8/28, -10/35

(ii) The four rational numbers equivalent to 5/-3 are,

= (5 × 2)/ (-3 × 2), (5 × 3)/ (-3 × 3), (5 × 4)/ (-3 × 4), (5 × 5)/ (-3× 5)

= 10/-6, 15/-9, 20/-12, 25/-15

(iii) The four rational numbers equivalent to 5/-3 are,

= (4 × 2)/ (9 × 2), (4 × 3)/ (9 × 3), (4 × 4)/ (9 × 4), (4 × 5)/ (9× 5)

= 8/18, 12/27, 16/36, 20/45

 

(i) We know that 3/4 is greater than 0 and less than 1.

∴ it lies between 0 and 1. It can be represented on the number line as,

(ii) We know that -5/8 is less than 0 and greater than -1.

∴ it lies between 0 and -1. It can be represented on the number line as,

(iii) Now, the above question can be written as,

= (-7/4) =

We know that (-7/4) is less than -1 and greater than -2.

∴ it lies between -1 and -2. It can be represented on the number line as,

(iv) We know that 7/8 is greater than 0 and less than 1.

∴ it lies between 0 and 1. It can be represented on the number line as,

 

 

(i) We have to check if the given pair represents the same rational number.

Then,

-7/21 = 3/9

-1/3 = 1/3

∵ -1/3 ≠ 1/3

∴ -7/21 ≠ 3/9

So, the given pair does not represent the same rational number.

(ii) We have to check if the given pair represents the same rational number.

Then,

-16/20 = 20/-25

-4/5 = 4/-5

∵ -4/5 = -4/5

∴ -16/20 = 20/-25

So, the given pair represents the same rational number.

(iii) We have to check if the given pair represents the same rational number.

Then,

-2/-3 = 2/3

2/3= 2/3

∵ 2/3 = 2/3

∴ -2/-3 = 2/3

So, the given pair represents the same rational number.

(iv) We have to check if the given pair represents the same rational number.

Then,

-3/5 = – 12/20

-3/5 = -3/5

∵ -3/5 = -3/5

∴ -3/5= -12/20

So, the given pair represents the same rational number.

(v) We have to check if the given pair represents the same rational number.

Then,

8/-5 = -24/15

8/-5 = -8/5

∵ -8/5 = -8/5

∴ 8/-5 = -24/15

So, the given pair represents the same rational number.

(vi) We have to check if the given pair represents the same rational number.

Then,

1/3 = -1/9

∵ 1/3 ≠ -1/9

∴ 1/3 ≠ -1/9

So, the given pair does not represent the same rational number.

(vii) We have to check if the given pair represents the same rational number.

Then,

-5/-9 = 5/-9

∵ 5/9 ≠ -5/9

∴ -5/-9 ≠ 5/-9

So, the given pair does not represent the same rational number.

 

(i) The given rational numbers can be simplified further,

Then,

= -4/3 … [∵ Divide both numerator and denominator by 2]

(ii) The given rational numbers can be simplified further,

Then,

= 5/9 … [∵ Divide both numerator and denominator by 5]

(iii) The given rational numbers can be simplified further,

Then,

= -11/18 … [∵ Divide both numerator and denominator by 4]

(iv) The given rational numbers can be simplified further,

Then,

= -4/5 … [∵ Divide both numerator and denominator by 2]

 

(i) The LCM of the denominators 7 and 3 is 21

∴ (-5/7) = [(-5 × 3)/ (7 × 3)] = (-15/21)

And (2/3) = [(2 × 7)/ (3 × 7)] = (14/21)

Now,

-15 < 14

So, (-15/21) < (14/21)

Hence, -5/7 [<] 2/3

(ii) The LCM of the denominators 5 and 7 is 35

∴ (-4/5) = [(-4 × 7)/ (5 × 7)] = (-28/35)

And (-5/7) = [(-5 × 5)/ (7 × 5)] = (-25/35)

Now,

-28 < -25

So, (-28/35) < (- 25/35)

Hence, -4/5 [<] -5/7

(iii) 14/-16 can be simplified further,

Then,

7/-8 … [∵ Divide both numerator and denominator by 2]

So, (-7/8) = (-7/8)

Hence, -7/8 [=] 14/-16

(iv) The LCM of the denominators 5 and 4 is 20

∴ (-8/5) = [(-8 × 4)/ (5 × 4)] = (-32/20)

And (-7/4) = [(-7 × 5)/ (4 × 5)] = (-35/20)

Now,

-32 > – 35

So, (-32/20) > (- 35/20)

Hence, -8/5 [>] -7/4

(v) The LCM of the denominators 3 and 4 is 12

∴ (-1/3) = [(-1 × 4)/ (3 × 4)] = (-4/12)

And (-1/4) = [(-1 × 3)/ (4 × 3)] = (-3/12)

Now,

-4 < – 3

So, (-4/12) < (- 3/12)

Hence, 1/-3 [<] -1/4

(vi) Since, (-5/11) = (-5/11)

Hence, 5/-11 [=] -5/11

(vii) Since every negative rational number is less than 0,

We get:

= 0 [>] -7/6

 

(i) The LCM of the denominators 3 and 2 is 6

(2/3) = [(2 × 2)/ (3 × 2)] = (4/6)

And (5/2) = [(5 × 3)/ (2 × 3)] = (15/6)

Now,

4 < 15

So, (4/6) < (15/6)

∴ 2/3 < 5/2

Hence, 5/2 is greater.

(ii) The LCM of the denominators 6 and 3 is 6

∴ (-5/6) = [(-5 × 1)/ (6 × 1)] = (-5/6)

And (-4/3) = [(-4 × 2)/ (3 × 2)] = (-12/6)

Now,

-5 > -12

So, (-5/6) > (- 12/6)

∴ -5/6 > -12/6

Hence, – 5/6 is greater.

(iii) The LCM of the denominators 4 and 3 is 12

∴ (-3/4) = [(-3 × 3)/ (4 × 3)] = (-9/12)

And (-2/3) = [(-2 × 4)/ (3 × 4)] = (-8/12)

Now,

-9 < -8

So, (-9/12) < (- 8/12)

∴ -3/4 < 2/-3

Hence, 2/-3 is greater.

(iv) The given fraction is like friction,

So, -¼ < ¼

Hence ¼ is greater,

(v) First, we have to convert mixed fractions into improper fractions,

= -23/7

= -19/5

Then,

The LCM of the denominators 7 and 5 is 35

∴ (-23/7) = [(-23 × 5)/ (7 × 5)] = (-115/35)

And (-19/5) = [(-19 × 7)/ (5 × 7)] = (-133/35)

Now,

-115 > -133

So, (-115/35) > (- 133/35)

∴
>

Hence,
is greater.

 

(i) The given rational numbers are in the form of like fractions,

Hence,

(-3/5)< (-2/5) < (-1/5)

(ii) To convert the given rational numbers into like fractions, we have to find the LCM,

The LCM of 3, 9, and 3 is 9

Now,

(-1/3)= [(-1 × 3)/ (3 × 9)] = (-3/9)

(-2/9)= [(-2 × 1)/ (9 × 1)] = (-2/9)

(-4/3)= [(-4 × 3)/ (3 × 3)] = (-12/9)

Clearly,

(-12/9) < (-3/9) < (-2/9)

Hence,

(-4/3) < (-1/3) < (-2/9)

(iii) To convert the given rational numbers into like fractions, we have to find LCM,

The LCM of 7, 2, and 4 is 28

Now,

(-3/7)= [(-3 × 4)/ (7 × 4)] = (-12/28)

(-3/2)= [(-3 × 14)/ (2 × 14)] = (-42/28)

(-3/4)= [(-3 × 7)/ (4 × 7)] = (-21/28)

Clearly,

(-42/28) < (-21/28) < (-12/28)

Hence,

(-3/2) < (-3/4) < (-3/7)

 

(i) The product of two rational numbers = (product of their numerator)/ (product of their denominator)

The above question can be written as (9/2) × (-7/4)

We have,

= (9×-7)/ (2×4)

= -63/8

(ii) The product of two rational numbers = (product of their numerator)/ (product of their denominator)

The above question can be written as (3/10) × (-9/1)

We have,

= (3×-9)/ (10×1)

= -27/10

(iii) The product of two rational numbers = (product of their numerator)/ (product of their denominator)

We have,

= (-6×9)/ (5×11)

= -54/55

(iv) The product of two rational numbers = (product of their numerator)/ (product of their denominator)

We have,

= (3×-2)/ (7×5)

= -6/35

(v) The product of two rational numbers = (product of their numerator)/ (product of their denominator)

We have,

= (3×2)/ (11×5)

= 6/55

(vi) The product of two rational numbers = (product of their numerator)/ (product of their denominator)

We have,

= (3×-5)/ (-5×3)

On simplifying,

= (1×-1)/ (-1×1)

= -1/-1

= 1

 

(i) We have:

= (5/4) – (11/4)

= [(5 – 11)/4] … [∵ denominator is same in both the rational numbers]

= (-6/4)

= -3/2 … [∵ Divide both numerator and denominator by 3]

(ii) Take the LCM of the denominators of the given rational numbers.

LCM of 3 and 5 is 15

Express each of the given rational numbers with the above LCM as the common denominator.

Now,

(5/3)= [(5×5)/ (3×5)] = (25/15)

(3/5)= [(3×3)/ (5×3)] = (9/15)

Then,

= (25/15) + (9/15) … [∵ denominator is same in both the rational numbers]

= (25 + 9)/15

= 34/15

(iii) Take the LCM of the denominators of the given rational numbers.

LCM of 10 and 15 is 30

Express each of the given rational numbers with the above LCM as the common denominator.

Now,

(-9/10)= [(-9×3)/ (10×3)] = (-27/30)

(22/15)= [(22×2)/ (15×2)] = (44/30)

Then,

= (-27/30) + (44/30) … [∵ denominator is same in both the rational numbers]

= (-27 + 44)/30

= (17/30)

(iv) We have,

= 3/11 + 5/9

Take the LCM of the denominators of the given rational numbers.

LCM of 11 and 9 is 99

Express each of the given rational numbers with the above LCM as the common denominator.

Now,

(3/11)= [(3×9)/ (11×9)] = (27/99)

(5/9)= [(5×11)/ (9×11)] = (55/99)

Then,

= (27/99) + (55/99) … [∵ denominator is same in both the rational numbers]

= (27 + 55)/99

= (82/99)

(v) We have

= -8/19 – 2/57

Take the LCM of the denominators of the given rational numbers.

LCM of 19 and 57 is 57

Express each of the given rational numbers with the above LCM as the common denominator.

Now,

(-8/19)= [(-8×3)/ (19×3)] = (-24/57)

(-2/57)= [(-2×1)/ (57×1)] = (-2/57)

Then,

= (-24/57) – (2/57) … [∵ denominator is same in both the rational numbers]

= (-24 – 2)/57

= (-26/57)

(vi) We know that any number or fraction is added to zero, the answer will be the same number or fraction.

Hence,

= -2/3 + 0

= -2/3

(vii) First, we have to convert mixed fractions into improper fractions.

== -7/3

== 23/5

We have, -7/3 + 23/5

Take the LCM of the denominators of the given rational numbers.

LCM of 3 and 5 is 15

Express each of the given rational numbers with the above LCM as the common denominator.

Now,

(-7/3)= [(-7×5)/ (3×5)] = (-35/15)

(23/5)= [(23×3)/ (15×3)] = (69/15)

Then,

= (-35/15) + (69/15) … [∵ denominator is same in both the rational numbers]

= (-35 + 69)/15

= (34/15)

 

(i) Take the LCM of the denominators of the given rational numbers.

LCM of 24 and 36 is 72

Express each of the given rational numbers with the above LCM as the common denominator.

Now,

(7/24)= [(7×3)/ (24×3)] = (21/72)

(17/36)= [(17×2)/ (36×2)] = (34/72)

Then,

= (21/72) – (34/72) … [∵ denominator is same in both the rational numbers]

= (21 – 34)/72

= (-13/72)

(ii) We can also write -6/21 = -2/7

= 5/63 – (-2/7)

We have,

= 5/63 + 2/7

Take the LCM of the denominators of the given rational numbers.

LCM of 63 and 7 is 63

Express each of the given rational numbers with the above LCM as the common denominator.

Now,

(5/63)= [(5×1)/ (63×1)] = (5/63)

(2/7)= [(2×9)/ (7×9)] = (18/63)

Then,

= (5/63) + (18/63) … [∵ denominator is same in both the rational numbers]

= (5 + 18)/63

= 23/63

(iii) We have,

= -6/13 + 7/15

LCM of 13 and 15 is 195

Express each of the given rational numbers with the above LCM as the common denominator.

Now,

(-6/13)= [(-6×15)/ (13×15)] = (-90/195)

(7/15)= [(7×13)/ (15×13)] = (91/195)

Then,

= (-90/195) + (91/195) … [∵ denominator is same in both the rational numbers]

= (-90 + 91)/195

= (1/195)

(iv) Take the LCM of the denominators of the given rational numbers.

LCM of 8 and 11 is 88

Express each of the given rational numbers with the above LCM as the common denominator.

Now,

(-3/8)= [(-3×11)/ (8×11)] = (-33/88)

(7/11)= [(7×8)/ (11×8)] = (56/88)

Then,

= (-33/88) – (56/88) … [∵ denominator is same in both the rational numbers]

= (-33 – 56)/88

= (-89/88)

(v) First, we have to convert the mixed fraction into an improper fraction,

–
= -19/9

We have, -19/9 – 6

Take the LCM of the denominators of the given rational numbers.

LCM of 9 and 1 is 9

Express each of the given rational numbers with the above LCM as the common denominator.

Now,

(-19/9)= [(-19×1)/ (9×1)] = (-19/9)

(6/1)= [(6×9)/ (1×9)] = (54/9)

Then,

= (-19/9) – (54/9) … [∵ denominator is same in both the rational numbers]

= (-19 – 54)/9

= (-73/9)

 

(i) We have,

= (-4/1) × (3/2) … [∵ reciprocal of (2/3) is (3/2)]

The product of two rational numbers = (product of their numerator)/ (product of their denominator)

= (-4×3) / (1×2)

= (-2×3) / (1×1)

= -6

(ii) We have,

= (-3/5) × (1/2) … [∵ reciprocal of (2/1) is (1/2)]

The product of two rational numbers = (product of their numerator)/ (product of their denominator)

= (-3×1) / (5×2)

= -3/10

(iii) We have,

= (-4/5) × (1/-3) … [∵ reciprocal of (-3) is (1/-3)]

The product of two rational numbers = (product of their numerator)/ (product of their denominator)

= (-4× (1)) / (5× (-3))

= -4/-15

= 4/15

(iv) We have,

= (-1/8) × (4/3) … [∵ reciprocal of (3/4) is (4/3)]

The product of two rational numbers = (product of their numerator)/ (product of their denominator)

= (-1×4) / (8×3)

= (-1×1) / (2×3)

= -1/6

(v) We have,

= (-2/13) × (7/1) … [∵ reciprocal of (1/7) is (7/1)]

The product of two rational numbers = (product of their numerator)/ (product of their denominator)

= (-2×7) / (13×1)

= -14/13

(vii) We have,

= (-7/12) × (13/-2) … [∵ reciprocal of (-2/13) is (13/-2)]

The product of two rational numbers = (product of their numerator)/ (product of their denominator)

= (-7× 13) / (12× (-2))

= -91/-24

= 91/24

(vii) We have,

= (3/13) × (65/-4) … [∵ reciprocal of (-4/65) is (65/-4)]

The product of two rational numbers = (product of their numerator)/ (product of their denominator)

= (3×65) / (13× (-4))

= 195/-52

= -15/4