Find the number of digits in 8^10. (Given log10 2 = 0.3010)
Aptitude
Logarithm
Difficulty: Easy
Choose an option
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A19
-
B20
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C17
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D10
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ENone of these
Answer
Correct Answer: 10
Explanation
Introduction / Context:Digit count problems rely on logarithms. If N > 0, then the number of decimal digits is floor(log10 N) + 1. We are given log10 2, which lets us evaluate powers of 2 efficiently.
Given Data / Assumptions:
- N = 8^10.
- 8 = 2^3, so 8^10 = (2^3)^10 = 2^30.
- log10 2 = 0.3010 (approximation sufficient for digit counting).
Concept / Approach:
- Compute log10(2^30) = 30 * log10 2.
- Use the digit-count formula: digits = floor(log10 N) + 1.
Step-by-Step Solution:
log10(8^10) = log10(2^30) = 30 * 0.3010 = 9.03Digits = floor(9.03) + 1 = 9 + 1 = 10Verification / Alternative check:Since 10^9 = 1,000,000,000 and 10^10 = 10,000,000,000, and 8^10 ≈ 1.07 × 10^9, it lies between 10^9 and 10^10, confirming 10 digits.
Why Other Options Are Wrong:
- 19, 17, 20 misapply the digit formula or misuse log10 2.
- “None of these” is incorrect because 10 is exact.
Common Pitfalls:
- Forgetting to add 1 after flooring log10 N.
Final Answer:10