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MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8 PDF Download

Q1: 10 meters of cloth cost Rs 1000. What will 4 meters cost?
(a) Rs 400
(b) Rs 800
(c) Rs 200
(d) Rs 100

MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8  View Answer

Ans: (a)
10/1000 = 4/x
= x = 400

Q2: If x = 20 and y = 40, then x and y are:
(a) Directly proportional
(b)  Inversely proportional
(c) Neither directly nor inversely proportional
(d) Cannot be determined 

MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8  View Answer

Ans: (a)
x = 20 and y = 40
Clearly, 40 = 2 x 20
y = 2x
y∝x, where 2 is the proportionality constant.

Q3: If x and y are directly proportional, then which of the following is correct?
(a) x+y=constant
(b) x-y=constant
 (c) xy=constant
(d) x/y=constant 

MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8  View Answer

Ans: (d)
x∝y
x=ky
k=x/y, where k is a constant.

Q4: The weight of 12 sheets of thick paper is 40 grams, how many sheets of the same paper would weigh 2500 grams?
(a) 750
(b) 800
(c) 850
(d) 950 

MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8  View Answer

Ans: (a)
For 12 sheets, the weight of the paper is 40 grams
Let a number of sheets for 2500 is x.
Using direct proportion concept:
12/40 = x/2500
x=(12×2500)/40
x=750

Q5: If x and y are inversely proportional, then which one is true?
(a) x1/y1 = x2/y2
(b) x1 /x2 = y1/y2
(c) x1 /x2 = y2/y1
(d) x1 .x2 = y1.y2 

MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8  View Answer

Ans: (c)
∝1/y
x=k(1/y)
xy=k
x1y= x2y2
x1/x= y2/y1

Q6: If 12 workers can build a wall in 50 hours, how many workers will be required to do the same work in 40 hours?
(a) 10
(b) 13
(c) 14
(d) 15 

MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8  View Answer

Ans: (d)
12 × 50 = x × 40
x = (12×50)/40  
= 15

Q7: If 300 Kg of coal cost 6000₹, then find the cost of 120 kg of coal?
(a) 1200₹
(b) 2400₹
(c) 3200₹
(d) 4200₹ 

MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8  View Answer

Ans: (b)
total weight =300kg
cost of 1 kg = 6000/300
= 20rupees 120kg
= 20 × 120 = 2400rupees

Q8: If it takes 40 days for 120 men to complete a work, how long will it take for 80 men to complete the same work?
(a) 50 days
(b) 60 days
(c) 80 days
(d) 100 days

MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8  View Answer

Ans: (b)
40 × 120 = 80 × x  
⇒ x = 60

Q9: A car takes 18 hours to ride 720 kilometers. Time taken by the car to travel 360 kilometers is:
(a) 10 hours
(b) 11 hours
(c) 9 hours
(d) 16 hours

MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8  View Answer

Ans:  (c)
720/18 = 360/x
x = 9 hours

Q10: The scale of a map is given as 1: 300. Two cities are 4 km apart on the map. The actual distance between them is:
(a) 1000 km
(b) 1100 km
(c) 1200 km
(d) 1300 km 

MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8  View Answer

Ans:  (c)
1 : 300 = x : y
1/300 = 4/y
y = 4 x 300 = 1200
Hence, the distance between the two cities is 1200 km.

The document MCQ (with Solutions): Direct and Inverse Proportions | Mathematics (Maths) Class 8 is a part of the Class 8 Course Mathematics (Maths) Class 8.
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FAQs on MCQ (with Solutions): Direct and Inverse Proportions - Mathematics (Maths) Class 8

1. How can direct and inverse proportions be distinguished?
Ans. In direct proportion, as one quantity increases, the other also increases at a constant rate. In contrast, in inverse proportion, as one quantity increases, the other decreases at a constant rate.
2. What is the relationship between direct proportion and inverse proportion?
Ans. Direct proportion occurs when two quantities increase or decrease together, while inverse proportion happens when one quantity increases as the other decreases, or vice versa.
3. How can direct and inverse proportions be represented mathematically?
Ans. Direct proportion can be represented as y = kx, where y is the dependent variable, x is the independent variable, and k is the constant of proportionality. Inverse proportion can be represented as xy = k, where x and y are the two quantities and k is the constant of proportionality.
4. Can a relationship exhibit both direct and inverse proportions simultaneously?
Ans. No, a relationship cannot exhibit both direct and inverse proportions simultaneously because they represent opposite trends in how two quantities change in relation to each other.
5. How can direct and inverse proportions be applied in real-life scenarios?
Ans. Direct and inverse proportions are commonly used in various real-life situations such as time and speed, work and time, pressure and volume, etc., to understand how changes in one quantity affect another.
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