SHORT ANSWER TYPE QUESTIONS :-
31. Write the additive inverse of 19/-6.
32. Mention the rational number that has no reciprocal.
33. Define a rational number.
34. Solve 7x – 12 = 16.
35. Solve 3 (x - 4) = 21
36. What is the sum of all interior angles of a quadrilateral ?
37. Name the quadrilateral that has one pair of parallel sides.
38. Name the parallelogram in which one of its angle is 90˚.
39. How many diagonals does a regular hexagon has?
40. angle A and angle B are two adjacent angles of a parallelogram. If angle A = 70˚, then what is the measure Of angle B?
Answers
Answer:
1.1
Question 1:
Using appropriate properties, find:
(i) -2/3 * 3/5 + 5/2 – 3/5 * 1/6 (ii) 2/5 * (3/-7) – 1/6 * 3/2 + 1/14 * 2/5
Answer:
(i) -2/3 * 3/5 + 5/2 – 3/5 * 1/6
= -2/3 * 3/5 – 3/5 * 1/6 + 5/2 [Using associative property]
= 3/5 * (-2/3 – 1/6) + 5/2 [Using distributive property]
= 3/5 * {(-4 - 1)/6} + 5/2 [LCM (3, 2) = 6]
= 3/5 * (-5/6) + 5/2
= -3/6 + 5/2
= -1/2 + 5/2
= (-1 + 5)/2
= 4/2
= 2
(ii) 2/5 * (3/-7) – 1/6 * 3/2 + 1/14 * 2/5
= 2/5 * (-3/7) + 1/14 * 2/5 – 1/6 * 3/2 [Using associative property]
= 2/5 * (-3/7 + 1/14) – 1/2 * 1/2 [Using distributive property]
= 2/5 * {(-6 + 1)/14} – 1/4 [LCM (7, 14) = 14]
= 2/5 * (-5/14) – 1/4
= -1/7 – 1/4
= (-4 -7)/28 [LCM (7, 4) = 28]
= -11/28
(i) Putting x = -13/17 in -(-x) = x, we get
=> -{-(-13/17)} = -13/17
=> -(13/17) = -13/17
=> -13/17 = -13/17
=> LHS = RHS
Hence, verified.
Question 4:
Find the multiplicative inverse of the following:
(i) -13 (ii) -13/19 (iii) 1/5 (iv) (-5/8)*(-3/7) (v) -1 * (-2/5) (vi) -1
Answer:
We know that multiplicative inverse of a rational number a is 1/a such that a * 1/a = 1
(i) Multiplicative inverse of -13 = -1/13
(ii) Multiplicative inverse of -13/19 = -19/13
(iii) Multiplicative inverse of 1/5 = 5
(iv) (-5/8)*(-3/7) = (5 * 3)/(8 * 7) = 15/56
Multiplicative inverse of 15/56 = 56/15
(v) -1 * (-2/5) = 2/5
Multiplicative inverse of 2/5 = 5/2
(vi) Multiplicative inverse of -1 = 1/-1 = -1
Question 5:
Name the property under multiplication used in each of the following:
(i) -4/5 * 1 = 1 * -4/5
(ii) -13/17 * -2/7 = -2/7 * -13/17
(iii) -19/29 * 29/-19 = 1
Answer:
(i) 1 is the multiplicative identity.
(ii) Commutative property.
(iii) Multiplicative Inverse property.
Exercise 1.2
Question 1:
Represent these numbers on the number line:
(i) 7/4 (ii) -5/6
Answer:
(i) 7/4 = 1
Class_8_RationalNumbers_NumberLine
Here, P is 1
(ii)- 5/6
Class_8_RationalNumbers_NumberLine1
Here, M is -5/6
Question 2:
Represent -2/11, -5/11, -9/11 on the number line.
Answer:
Here, B = -2/11, C = -5/11, D = -9/11
Class_8_RationalNumbers_NumberLine2
Question 3:
Write five rational numbers which are smaller than 2.
Answer:
2 can be represented as 14/7
Hence, five rational numbers smaller than 2 are:
13/7, 12/7, 11/7, 10/7 and 9/7
Question 4:
Find ten rational numbers between -2/5 and 1/2
Answer:
Given rational numbers are -2/5 and 1/2
Here, LCM of 5 and 2 is 10
So, -2/5 = (-2 * 2)/(5 * 2) = -4/10
and 1/2 = (1 * 5)/(2 * 5) = 5/10
Again, -4/10 = (-4 * 2)/(10 * 2) = -8/20
and 5/10 = (5 * 2)/(10 * 2) = 10/20
Hence, ten rational numbers between -2/5 and 1/2 are:
-7/20, -6/20, -5/20, -7/20, -4/20, -3/20, -2/20, -1/20, 0, 1/20, 2/20
Question 5:
Find five rational numbers between:
(i) 2/3 and 4/5 (ii) -3/2 and 5/3 (iii) 1/4 and 1/2
Answer:
(i) Given rational numbers are 2/3 and 4/5
Here, LCM of 3 and 5 is 15
So, 2/3 = (2 * 5)/(3 * 5) = 10/15
and 4/5 = (4 * 3)/(5 * 3) = 12/15
Again, 10/15 = (10 * 4)/(15 * 4) = 40/60
and 4/5 = (12 * 4)/(15 * 4) = 48/60
Hence, ten rational numbers between 2/3 and 4/5 are:
14/60, 42/60, 43/60, 44/60, 45/60
(ii) Given rational numbers are -3/2 and 5/3
Here, LCM of 2 and 3 is 6
So, -3/2 = (-3 * 3)/(2 * 3) = -9/6
and 5/3 = (5 * 2)/(3 * 2) = 10/6
Hence, ten rational numbers between -3/2 and 5/3 are:
-8/7, -7/6, 0, 1/6, 2/6
(iii) Given rational numbers are 1/4 and 1/2
Here, LCM of 4 and 2 is 4
So, 1/4 = (1 * 1)/(4 * 1) = 1/4
and 1/2 = (1 * 2)/(2 * 2) = 2/4
Again, 1/4 = (1 * 8)/(4 * 8) = 8/32
and 2/4 = (2 * 8)/(4 * 8) = 16/32
Hence, ten rational numbers between 1/4 and 1/2 are:
9/32, 10/32, 11/32, 12/32, 1/32
Question 6:
Write 5 rational numbers greater than -2.
Answer:
-2 can be represented as -14/2
Therefore, five rational numbers greater than -2 are:
-13/7, -12/7, -11/7, -10/7, -9/7
Question 7:
Find ten rational numbers between 3/5 and 3/4.
Answer:
(iii) Given rational numbers are 3/5 and 3/4
Here, LCM of 5 and 4 is 20
So, 3/5 = (3 * 4)/(5 * 4) = 12/20
and 3/4 = (3 * 5)/(4 * 5) = 15/20
Again, 12/20 = (12 * 8)/(20 * 8) = 96/160
and 15/20 = (15 * 8)/(20 * 8) = 120/160
Hence, ten rational numbers between 3/5 and 3/4 are:
97/160, 98/160, 99/160, 100/160, 101/160, 102/160, 103/160, 104/160, 105/160, 106/160,
Explanation:
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Answer:
31)19/6
32)0
33)Number that can be represented as the quotient p/q of two integers such that q ≠ 0
34)x=4
35)x=11
36)360°
37) Trapezium
38) Rectangle
39)9
40)110°