If log10 2 = 0.3010, the value of log10 80 is:
202320252024
If log10 2 = 0.3010, the value of log10 80 is:
- A.
1.6020
- B.
1.9030
- C.
3.9030
- D.
None
Attempted by 2 students.
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Correct answer: B
Two logarithm laws apply here: the product rule log(a×b) = log a + log b, and the power rule log(an) = n·log a. Together they let the logarithm of a number be built up from the logarithms of its factors.
Factor 80 as a power of 2 times 10: 80 = 23 × 10.
Apply the product rule: log1080 = log10(23) + log1010.
Apply the power rule to the first term: log10(23) = 3×log102.
log1010 = 1, since 10 raised to the power 1 equals 10.
Substitute log102 = 0.3010: 3×0.3010 = 0.9030.
Add the two parts: 0.9030 + 1 = 1.9030.
Cross-check: log1080 must lie between log1010 = 1 and log10100 = 2, and closer to 2 since 80 is nearer 100 than 10 on a log scale — 1.9030 fits comfortably in that range.
