# Beginners question: Factorised expression, not sure how book got the answer

I have an expression:

$2a^3 / 3a^2 * 6a^5$

and my book gives the answer:

$4a^6$

I get where the $a^6$ is from but how is the $4$ worked out?

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$\frac{2}{3}\times 6=\frac{12}{3}=4$. – André Nicolas Mar 28 '12 at 14:10
Wow, that's obvious. Thanks, I don't know why that didn't even occur to me... must be having a bad day! – penpen Mar 28 '12 at 14:13
Please include parentheses in expressions like $a/b*c$. Many people mean $a/(b*c)$ when they write it. You didn't, but it makes it easier on the reader to be sure. It is true, when you quote a book, you should quote exactly. – Ross Millikan Mar 28 '12 at 14:31
Thanks for the tip. It was written in the book exactly like that but with a "÷" instead of a /. – penpen Mar 28 '12 at 14:55

Because its $2\cdot6/3 = 12/3=4$. That's without the $a$'s and its exponents.