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Magical Pond
Last updated at Aug. 18, 2025 by Teachoo
Class 8 (Ganita Prakash & Old NCERT)
Chapter 2 Class 8 - Power Play (Ganita Prakash)
- Basic Concepts & Formulas
- Introduction
- Exponential Notation and Operations
- Figure it out - Page 22, 23
- The Stones that Shine ...
- Formulas of Exponents
-
Magical Pond
- Multiplying & Dividing two numbers with Same Power
- Combinations
- The Other Side of Powers
- Power Lines
- Powers of 10
- Scientific Notation
- Did you ever Wonder..
- Linear Growth vs Exponential Growth
- Getting a sense of Large Numbers
- A Pinch of History
- Figure it out - Page 44, 45
Transcript
Magical PondIn the middle of a beautiful, magical pond lies a bright pink lotus. The number of lotuses doubles every day in this pond. After 30 days, the pond is completely covered with lotuses. On which day was the pond half full? Write the number of lotuses (in exponential form) when the pond was (i) fully covered (ii) half covered Now, Number of lotus after Day 1 = 1 × 2 Number of lotus after Day 2 = 2 × 2 = 22 Number of lotus after Day 3 = 22 × 2 = 22+1 = 23 Number of lotus after Day 4 = 23 × 2 = 23+1 = 24 Number of lotus on Day 5 = 24 × 2 = 24+1 = 25 ……. Number of lotus after Day 28 = 228 Number of lotus after Day 29 = 229 Number of lotus after Day 30 = 230 Since pond if completely covered on Day 30, and lotus doubles everyday… Pool is half-filled on Day 29 Thus, Number of lotuses when pond was fully covered = Number of lotus on Day 30 = 230 And, Number of lotuses when pond was half covered = Number of lotus on Day 29 = 229
