What is 2187 divided by 9 to the power 3?

Which of the following parabolas opens down?

You can ride your bike around your block 6 times and the whole neighborhood 5 times in 16 minutes. you can ride your bike around your block 3 times and the whole neighborhood 10 times in 23 minutes. how long does it take you to ride around the neighborhood?

What is the benefit of converting measures in a ratio to the same unit