Class 8 Maths Chapter 13 Direct and Inverse Proportions MCQs

Class 8 Maths Chapter 13 (Direct and Inverse Proportions) MCQs are available online for students, with solved answers. These objective questions are designed by our subject experts, according to CBSE syllabus (2020-2021) 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.

MCQs on Class 8 Direct and Inverse Proportions

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

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