1. What is the cube root of 8, written as ?
- A2
- B3
- C4
- D8
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Answer: A) 2
2 x 2 x 2 = 8, so = 2.
Class 8 Finding Cube Roots — practice questions with answers
Cubes and Roots · 5 sample questions from the school syllabus. Try each one, then open the answer and the worked solution.
2. Find .
- A-3
- B-6
- C-4
- D-2
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Answer: A) -3
(-3)³ = -27, so = -3.
3. A cubical water tank has a volume of 1331 cubic metres.
The length of each edge of the tank equals the cube root of its volume.
What is the length of one edge in metres?
The length of each edge of the tank equals the cube root of its volume.
What is the length of one edge in metres?
- A11 m
- B13 m
- C12 m
- D21 m
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Answer: A) 11 m
Edge = . 11³ = 1331, so the edge is 11 m.
4. Two cubes have volumes 64 cubic cm and 512 cubic cm.
The ratio of their edge lengths equals the ratio of their cube roots.
What is the ratio (smaller : larger) of their edges?
The ratio of their edge lengths equals the ratio of their cube roots.
What is the ratio (smaller : larger) of their edges?
- A1 : 2
- B1 : 8
- C1 : 4
- D2 : 1
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Answer: A) 1 : 2
Edges = = 4 and = 8. Ratio = 4 : 8 = 1 : 2.
5. Three friends Arjun, Bina and Charu each think of a number.
Arjun's number cubes to 1000, Bina's cubes to 8000, and Charu's cubes to 27000.
What is the sum of the three original numbers?
Arjun's number cubes to 1000, Bina's cubes to 8000, and Charu's cubes to 27000.
What is the sum of the three original numbers?
- A60
- B36000
- C100
- D600
Show answer
Answer: A) 60
= 10, = 20, = 30. Sum = 10 + 20 + 30 = 60.
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