"Seven tenths?"

Multiplying by 5 \(ten times\) is about the same as multiplying by 10 \(seven times\), so multiplying by five \(once\) is about the same as multiplying by 10 \(one seventh of a time\)\. Thus, $~$\\log\_{10}(500)$~$ is approximately 2\.7: That's how many times you need to multiply 1 by 10 to get 500\.

Seven tenths?