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AMC 12 Mock Exam 3 Problem 7

Problem 7 of 25

What is the value of (log⁡29)(log⁡316)(log⁡425)(log⁡58)(\log_2 9)(\log_3 16)(\log_4 25)(\log_5 8)?

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Solution

We have log⁡29=2log⁡23\log_29=2\log_23, log⁡316=4log⁡32\log_316=4\log_32, log⁡425=log⁡25log⁡4=log⁡25\log_425=\frac{\log 25}{\log4}=\log_25, and log⁡58=3log⁡52\log_58=3\log_52. Since log⁡23⋅log⁡32=1\log_23\cdot\log_32=1 and log⁡25⋅log⁡52=1\log_25\cdot\log_52=1, the product is 2⋅4⋅3=242\cdot4\cdot3=\boxed{24}.

Tagged: logarithm products, change of base