Class 8 Maths Chapter 2 Power Play Visual Infographic | NCF 2023 Ganita Prakash
Chapter 2: Power Play
Laws of Exponents, Exponential vs. Linear Growth, Scientific Notation & Ancient Number Systems
⚡ Laws of Exponents
• na × nb = na+b
• na ÷ nb = na−b (n ≠ 0)
(na)b = (nb)a = nab. Powers multiply directly.
• n0 = 1 (n ≠ 0)
• n−a = 1 / na and na = 1 / n−a
๐ฌ Scientific Notation & Distributive Powers
1. Distributing Powers:
• ma × na = (mn)a
• ma ÷ na = (m/n)a (n ≠ 0)
2. Standard Scientific Form:
Written as x × 10y, where 1 ≤ x < 10 and y is an integer. The exponent y defines the scale/magnitude.
3. Expanded Place Value with Powers:
561.903 = 5×102 + 6×101 + 1×100 + 9×10−1 + 0×10−2 + 3×10−3.
๐ Multiplicative Growth
A 0.001 cm sheet doubles each fold (thickness = 0.001 × 2k cm). At 46 folds, thickness exceeds 7,00,000 km (reaching the Moon!).
• Linear: Additive (+20 cm step → 1.92 billion steps to Moon).
• Exponential: Multiplicative (×2 each step → only 46 steps).
• 5-digit PIN: 105 = 1,00,000 codes.
• 6-slot letter lock (A-Z): 266 = 308,915,776 combinations.
๐️ Ancient Indian Number Names & Cosmic Scales
• Indian Number Scale (Powers of 100): Lakh (105), Crore (107), Arab (109), Kharab (1011), Neel (1013), Padma (1015), Shankh (1017), Maha-shankh (1019).
• Ancient Buddhist & Jain Texts: Lalitavistara (1st BCE) names powers up to Tallakshana (1053). Amalasiddhi lists up to 1096 (Dasha-ananta) and Kฤccฤyana lists up to 10140 (Asankhyeya).
• Googol & Googolplex: 1 Googol = 10100. 1 Googolplex = 10Googol = 10(10100). Total atoms in observable universe ≈ 1078 to 1082.
• Cosmic Time Scales: 109 seconds ≈ 31.7 years. 1017 seconds ≈ 3.17 billion years. Age of Earth = 4.5 billion years; Age of Universe = 13.8 billion years.
⚠️ Common Exponent Traps
Trap 1: Negative Base vs. Negative Exponent
A negative exponent indicates a reciprocal, NOT a negative answer: 2−4 = 1/24 = 1/16. Meanwhile, (−2)4 = +16 (even power) and (−2)5 = −32 (odd power).
Trap 2: Adding Bases When Multiplying
24 × 23 = 27 (add exponents, keep base same). It is strictly NOT 47! Similarly, 109 + 109 = 2 × 109, NOT 1018.