We have  \[\frac{(10r^3)(4r^6)}{8r^4}= \frac{40r^{3+6}}{8r^4} = \frac{40}{8}r^{3+6-4} = \boxed{5r^5}.\]
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Simplify $\frac{(10r^3)(4r^6)}{8r^4}$.
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
5r^5
Simplify $\frac{(10r^3)(4r^6)}{8r^4}$.
test