2019 · Q77
What is the number of digits in 7²⁵, 8²³ and 9²⁰ respectively? [Given log₁₀2 = 0.301, log₁₀3 = 0.477, log₁₀7 = 0.845]
Elementary MathematicsAlgebra
- A21, 20, 19
- B20, 19, 18
- C22, 21, 20
- D22, 20, 21
Explanation
Digits = floor(n.log10)+1. 7^25: 25x0.845 = 21.125 -> 22. 8^23: 69x0.301 = 20.769 -> 21. 9^20: 40x0.477 = 19.08 -> 20.