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If 5x=6y=3075^x = 6^y = 30^7, then what is the value of 1x+1y\frac{1}{x}+\frac{1}{y} ?

Solution

Correct Option: 2

5x=3075^x=30^7 gives x=7log30log5x=\frac{7\log 30}{\log 5}, so 1x=log57log30\frac{1}{x}=\frac{\log 5}{7\log 30}. Similarly 1y=log67log30\frac{1}{y}=\frac{\log 6}{7\log 30}. Sum =log5+log67log30=log307log30=17=\frac{\log 5+\log 6}{7\log 30}=\frac{\log 30}{7\log 30}=\frac{1}{7}.

Note: The chosen option 3 (15) is incorrect; the correct answer is option 2 (1/7).

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