Class 8 Maths MCQ – Cubes and Cube Roots

This set of Class 8 Maths Chapter 7 Multiple Choice Questions & Answers (MCQs) focuses on “Cubes and Cube Roots”. These MCQs are created based on the latest CBSE syllabus and the NCERT curriculum, offering valuable assistance for exam preparation.

1. What can be general formula to find cube of any number?
a) (a±b)3
b) a2
c) (a±b)2
d) b
View Answer

Answer: a
Explanation: The general formula of finding square of any number is (a±b)3. We need to express the given number whose cube needs to be found in the form of (a±b). We can then use the formula:
(a±b)3= a3 ± 3a2 b+3ab2 ± b3.

2. What form can be used to find cube of 13?
a) (10+3)3
b) (10-3)3
c) (10+3)
d) (10-3)
View Answer

Answer: a
Explanation: The number 13 can be represented in form 10 + 3, this will help us to calculate the cube of the number. This method would help us eliminate the traditional method of multiplying the number with itself.

3. 893 = ____
a) (90-1)2
b) (90-1)3
c) 12
d) 92
View Answer

Answer: b
Explanation: If we must find the cube of the 89, we use the second variation i.e.(90-1)3. This would help us and make the calculations easier instead of multiplying the number with itself thrice.
Therefore (90-1)3 = 903 – 3 × 902 × 1 + 3 × 90 × 12 – 13
Therefore (90-1)3 = 729000 – 24300 + 270 – 1
Therefore (90-1)3 = 704969.
advertisement
advertisement

4. Find the cube of 32.
a) 32768
b) 37968
c) 32769
d) 35937
View Answer

Answer: a
Explanation: To find cube of 32, we would use the form
Therefore (30+2)3 = 303 + 3 × 302 × 2 + 3 × 30 × 22 + 23
Therefore (30+2)3 = 27000 + 5400 + 360 + 8
Therefore (30+2)3 = 32768

5. Calculate the cube of 201.
a) 8120604
b) 8120609
c) 8120600
d) 8120601
View Answer

Answer: d
Explanation: In the multiple-choice question, we can eliminate three options by mere observation. The unit place of cube of 201 should be 1. The only option which has 1 in unit place is 8120601. The other options are incorrect by mere observation.
Sanfoundry Certification Contest of the Month is Live. 100+ Subjects. Participate Now!

6. 343 = _____
a) 39504
b) 39304
c) 35304
d) 34304
View Answer

Answer: b
Explanation: In order to calculate the cube of 34 we use the formula,
(a+b)3, where we consider a=30 and b=4
Therefore (30+4)3 = 303 + 3×302 × 4 + 3 × 30 × 42 + 43
Therefore (30+4)3 = 27000 + 10800 + 1440 + 64
Therefore (30+4)3 = 39304.

7. Which of below is not a perfect cube?
a) 125
b) 728
c) 729
d) 64
View Answer

Answer: b
Explanation: Perfect cube is formed when a natural number is multiplied to itself thrice. For example, 4 is a natural number which multiplied with itself thrice gives us 64. Hence, 64 is a perfect cube. But we do not have a natural number which multiplied with itself thrice gives us 728. Hence, 728 is not a perfect cube.
advertisement

8. How many perfect cubes exist between 1 and 100?
a) 4
b) 20
c) 16
d) 8
View Answer

Answer: a
Explanation: Perfect cube is formed when a natural number is multiplied to itself thrice. There are 4 perfect cubes between 1 and 100. They are 1, 8, 27, 64.

9. How many perfect cubes exist between 1 and 1000?
a) 5
b) 20
c) 10
d) 15
View Answer

Answer: a
Explanation: Perfect cube is formed when a natural number is multiplied to itself thrice. There are 10 perfect cubes between 1 and 1000. They are 1, 8, 27, 64, 125, 216, 343, 512, 729 and 1000.
advertisement

10. 573 = _____
a) 193753
b) 176452
c) 185193
d) 186743
View Answer

Answer: c
Explanation: In order to calculate the cube of 57 we use the formula,
(a-b)3, where we consider a=60 and b=3
Therefore (60-3)3 = 603 – 3 × 602 × 3 + 3 × 60 × 32 – 33
Therefore (60-3)3 = 216000 – 32400 + 1620 – 27
Therefore (60-3)3 = 185193.

More MCQs on Class 8 Maths Chapter 7:

To practice all chapters and topics of class 8 Mathematics, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

Subscribe to his free Masterclasses at Youtube & discussions at Telegram SanfoundryClasses.