Class 8 Maths Chapter 13 – Direct and Inverse Proportions MCQs Questions are available online for students, with solved answers. These objective questions are designed by our subject experts, according to CBSE syllabus (2022-2023) and NCERT guidelines. The chapter-wise multiple-choice questions are given at BYJU’S to make every student learn each chapter thoroughly and support them to score better. Also, learn important questions for class 8 Maths here.
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MCQs Questions on Class 8 Direct and Inverse Proportions with Answers
Multiple choice questions (MCQs) are given for Class 8 Direct and Inverse Proportions chapter. Students need to solve each question here and select the appropriate option.
1. 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
Answer: A
Explanation: x = 20 and y = 40
Clearly, 40 = 2 x 20
y=2x
y∝x, where 2 is the proportionality constant.
2. If x = 15 and y = 1/30, then x and y are:
A. Directly proportional
B. Inversely proportional
C. Neither directly nor inversely proportional
D. Cannot be determined
Answer: B
Explanation: x = 15, y = 1/30
1/30 = 1/(2 × 15)
y = 1/2x
Hence, y ∝ 1/x, where 1/2 is the proportionality constant.
3. 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
Answer: D
Explanation: x∝y
x=ky
k=x/y, where k is a constant.
4. If x and y are inversely proportional, then:
A. x+y=constant
B. x-y=constant
C. xy=constant
D. x/y=constant
Answer: C
Explanation: x∝1/y
x=k/y
xy=k
Where k is a constant.
5. If x∝y and x1=5,y1=210 and x2 = 2, then find y2?
A. 200
B. 84
C. 99
D. 70
Answer: B
Explanation: x∝y
x=ky
x/y=k
x1/y1 = x2/y2
5/210 = 2/y2
y2 = 84
6. If 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
Answer: A
Explanation: For 12 sheets, weight of paper is 40 grams
Let number of sheets for 2500 is x.
Using direct proportion concept:
12/40 = x/2500
x=(12×2500)/40
x=750
7. 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
Answer: C
Explanation: 1:300 = x : y
1/300 = 4/y
y = 4 x 300 = 1200
Hence, the distance between the two cities is 1200 km.
8. 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
Answer: C
Explanation: x∝1/y
x=k(1/y)
xy=k
x1y1=x2y2
x1/x2=y2/y1
9. 6 pipes are required to fill a tank in 1 hour 20 minutes. If we use 5 such types of pipes, how much time it will take to fill the tank?
A. 120 minutes
B. 96 minutes
C. 80 minutes
D. 85 minutes
Answer: B
Explanation: For 6 pipes, it takes 1 hour 20 minutes
1 hour 20 minutes = 60+20 = 80 minutes
For 5 pipes, let the time taken be x.
This is inverse proportion case:
80 × 6 = x × 5
x = 480/5 = 96
10. 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
Answer: D
Explanation: 12 × 50 = x × 40
x = (12×50)/40 = 15
11. A man walks 20 km in 5 hours. How much time it will take for him to walk 32 km?
A. 3 hours
B. 4 hours
C. 6 hours
D. 8 hours
Answer: D
Solution: Man walks 20 km in → 5 hours
That means it will take more time to walk 32 km. This is the case of direct proportion.
20/5 = 32/x
x = 32/4 = 8
12. If 300 Kg of coal cost 6000₹, then find the cost of 120 kg of coal?
A. 1200₹
B. 2400₹
C. 3200₹
D. 4200₹
Answer: B
Solution:
300/6000 = 120/x
x = 2400
13. Manvi types 200 words in 30 minutes. How many words she will type in 12 minutes?
A. 100
B. 80
C. 60
D. 50
Answer: B
Solution:
30/200 = 12/x
x = 12 x 200/30
x = 80
14. 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
Answer: B. 60 days
40 × 120 = 80 × x
⇒ x = 60
15. 6 pipes are required to fill a tank in 80 minutes. How long will it take if only 5 pipes of the same type are used?
A. 96 minutes
B. 102 minutes
C. 106 minutes
D. 108 minutes
Answer: A. 96 minutes
80 × 6 = x × 5
x = 96
16. If 12 labours can construct a road in 50 hours, how many labours will be required to construct the same road in 40 hours?
A. 10
B. 12
C. 14
D. 15
Answer: D. 15
12 × 50 = x × 40
x = (12 × 50)/40 = 15
17. If 100 students took 20 days to clean a garden. How many days it will take to clean the garden if 25 more students are added?
A. 10
B. 12
C. 16
D. 18
Answer: C. 16
100 × 20 = 125 × x
x = 16
18. If x = 10 and y = 20, then x and y are:
A. Directly proportional
B. Inversely proportional
C. Neither directly nor inversely proportional
D. Cannot be determined
Answer: A. Directly proportional
x = 10 and y = 20
y = 2 x 10 = 2x
Y is directly proportional to x, where 2 is the proportionality constant.
19. A car takes 18 hours to ride 720 kilometres. Time taken by the car to travel 360 kilometres is:
A. 10 hours
B. 11 hours
C. 9 hours
D. 16 hours
Answer: C. 9 hours
720/18 = 360/x
20. The perimeter of a square and its side is in:
A. Direct Proportion
B. Indirect Proportion
C. Neither direct nor indirect
D. Cannot be determined
Answer: A. Direct Proportion
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