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Question
If log 16 = a, log 9 = b and log 5 = c, evaluate the following in terms of a, b, c: log 720
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Solution
log16 = a, log9 = b and log5 = c
log42 = a, log32 = b and log5 = c
2log4 = a, 2log3 = b and log5 = c
`"log"4 = "a"/(2) , "log"3 = "b"/(2) and "log"5` = c
Consider, log720 = log(42 x 32 x 5)
= log42 + log32 + log5
= 2log4 + 2log3 + log5
= `2("a"/2) + 2 ("b"/2) + "c"`
= a + b + c.
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