Simplify $\frac{(10r^3)(4r^6)}{8r^4}$.
To simplify this fraction, I can use the properties of exponents and division to rewrite it. First, I can multiply the numerators and the denominators separately, using the product rule of exponents: $(10r^3)(4r^6) = 40r^{3+6}$ and $8r^4 = 8r^4$. So the fraction becomes $\frac{40r^9}{8r^4}$. Next, I can divide the coefficients and the variables separately, using the quotient rule of exponents: $\frac{40}{8} = 5$ and $\frac{r^9}{r^4} = r^{9-4}$. So the fraction simplifies to $5r^5$. 