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Question 4 - Figure it out - Page 16, 17 - Chapter 1 Class 8 - A Square and a Cube (Ganita Prakash)
Last updated at July 30, 2025 by Teachoo
Class 8 (Ganita Prakash & Old NCERT)
Chapter 1 Class 8 - A Square and a Cube (Ganita Prakash)
- Introduction
- Square Numbers
- Perfect Squares - and its Properties
- Perfect Squares - and its Patterns
- Square Root
- Smallest number multiply or divide to get perfect square
- Estimating Square Root
- Figure it out - Page 10, 11
- Cubic Numbers
- Perfect Cubes - and its Properties
- Perfect Cubes - and its Patterns
- Cube Root
- Smallest number multiply or divide to get perfect cube
- A pinch of History
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Figure it out - Page 16, 17
Transcript
Question 4 You are told that 1331 is a perfect cube. Can you guess without factorisation what its cube root is? Similarly, guess the cube roots of 4913, 12167, and 32768. This method works by looking at the last digit of the cube. For 1331: It ends in 1. The only digit whose cube ends in 1 is 1. The root is between 10 (103 = 1000) and 20 (203 = 8000), so the answer must be 11. For 4913: It ends in 3 The root must end in 7 (73 = 343). The root is between 10 and 20, so the answer must be 17. For 12167: It ends in 7. The root must end in 3 (33 = 27). The root is between 20 (203 = 8000) and 30 (303 = 27000), so the answer must be 23. For 32768: It ends in 8. The root must end in 2 (23 = 8). The root is between 30 and 40 (403 = 64000), so the answer must be 32.
