basic math problem relating to log thought my answer is not matching with the alternative

Question

$1/2 \log c = 0.915$. Calculate $c$.

It is a basic math problem but my answers are not matching with the alternatives.

but the answers is $0.15$.

use Tex to typeset your question – Nebo Alex Apr 11 '16 at 06:05 — Nebo Alex, Apr 11 '16 at 06:05

Arthur · Answer 1 · 2016-04-11T06:09:51.960

1

You went from $\log(c^{1/2})=0.915$ to $c^{1/2}=0.915$. That is not a valid transition.

$$ \frac12\log c=0.915\\ \log(c^{1/2})=0.915\\ c^{1/2}=10^{0.915}=8.22\\ c=8.22^2=67.6 $$

edited Apr 11 '16 at 06:09

answered Apr 11 '16 at 05:59

Arthur

im still stuck. How do i do it? thanks. – James George Apr 11 '16 at 06:02
@JamesGeorge Is your logarithm base ten or base $e$? – Arthur Apr 11 '16 at 06:03
the log has base 10. – James George Apr 11 '16 at 06:06
@JamesGeorge I added a solution to my answer. As you can see, $0.15$ is not the correct answer at all. You could've seen that just by calculating $1/2\log(0.15)=-0.41$. – Arthur Apr 11 '16 at 06:10

1 Answers1