How many cm in 92.4 inches?

Thank you!

Acircle has a circumference of 28.36 units what is the diameter of the circle

Starting at home, emily traveled uphill to the hardware store for 606060 minutes at just 666 mph. she then traveled back home along the same path downhill at a speed of 121212 mph. what is her average speed for the entire trip from home to the hardware store and back?

Which one is the correct answer, and why?