ad is a chord of a circle whose diameter is 20cm if ad is equal to 16 cm find distance of area from the centre of the circle

Acourt reporter is transcribing an accident report from germany. the report states that the driver was traveling 80 kilometers per hour. how many miles per hour was the driver traveling?

I'm confused on this could anyone me and show me what i need to do to solve it.

The sum of the speeds of two trains is 720.2 mph. if the speed of the first train is 7.8 mph faster than the second train, find the speeds of each.