Class 7 Maths

# Rational Numbers NCERT Exercise 9.2

Question 1: Find the sum:

(a) 5/4+(-11)/(4)

Answer: 5/4+(-11)/(4)=4/5-(11)/4

=(5-11)/4=-6/4=-3/2

(b) 5/3+3/5

Answer: 5/3+3/5

=(25+9)/(15)=(34)/(15)

(c) (-9)/(10)+(22)/(15)

Answer: (-9)/(10)+(22)/(15)

=(-27+44)/(30)=(17)/(30)

(d) (-3)/(-11)+5/9

Answer: (-3)/(-11)+5/9

=(3)/(11)+5/9

=(27+55)/(99)=(82)/(99)

(e) (-8)/(19)+(-2)/(57)

Answer: (-8)/(19)+(-2)/(57)

=(-8)/(19)-(2)/(57)

=(-24-2)/(57)=(-26)/(57)

(f) -2/3+0

Answer: When zero is added to any number, the value of number does not change.

-2/3+0=-2/3

(g) -2\1/3+4\3/5

Answer: -2\1/3+4\3/5=-7/3+(23)/(5)

=(-35+69)/(15)=(34)/(15)

Question 2: Find the value of following:

(a) (7)/(24)-(17)/(36)

Answer: (7)/(24)-(17)/(36)

=(21-34)/(72)=-(13)/(72)

(b) (5)/(63)-621

Answer: (5)/(63)-621

=(5-39123)/(63)=-(39118)/(63)

(c) (-6)/(13)-715

Answer: (-6)/(13)-715

=(-6-9295)/(13)=(-9301)/(13)

(d) (-3)/(8)-(7)/(11)

Answer: (-3)/(8)-(7)/(11)

=(-33-56)/(88)=-(89)/(88)

(e) -2\1/9-6

Answer: -2\1/9-6=-(19)/(9)-6

=(-19-54)/(9)=-(73)/(9)

Question 3: Find the product of following:

(a) 9/2xx(-7)/(4)

Answer: 9/2xx(-7)/(4)=-(63)/(8)

(b) (3)/(10)xx-9

Answer: (3)/(10)xx-9=-(27)/(10)

(c) -6/5xx(9)/(11)

Answer: -6/5xx(9)/(11)=-(54)/(55)

(d) 3/7xx(-2)/(5)

Answer: 3/7xx(-2)/(5)=-(6)/(35)

(e) (3)/(11)xx2/5

Answer: (3)/(11)xx2/5=(6)/(55)

(f) (3)/(-5)xx(-5)/(3)

Answer: (3)/(-5)xx(-5)/(3)=1

Question 4: Find the value of following:

(a) -4÷2/3

Answer: -4÷2/3

=4xx3/2=-6

(b) -3/5÷2

Answer: -3/5÷2

=-3/5xx1/2=(-3)/(10)

(c) -4/5÷(-3)

Answer: -4/5÷(-3)

=-4/5xx(-1)/(3)=(4)/(15)

(d) -1/8÷3/4

Answer: -1/8÷3/4

=-1/8xx4/3=-1/6

(e) -(2)/(13)÷1/7

Answer: -(2)/(13)÷1/7

=-(2)/(13)xx7/1=-(14)/(13)

(f) -(7)/(12)÷(-2)/(13)

Answer: -(7)/(12)÷(-2)/(13)

=-(7)/(12)xx(-13)/(2)=(91)/(24)

(g) (3)/(13)÷(-4)/(65)

Answer: (3)/(13)÷(-4)/(65)

=(3)/(13)xx(-65)/(4)=-(15)/(4)