Can you explain these four questions the rate and unit rate

What is the exact area of a circle with a diameter of 50 centimeters? a.87.9 square centimeters b.379.9 square centimeters c.1962.5 square centimeters d.4923.5 square centimeters

Asap the total attendance for all of a baseball league in 2012 was about 7.5×107 fans, while the attendance for the tornadoes in 2012 was about 1.5×106 fans. about how many times more was the attendance for the entire baseball league than the attendance for just the tornadoes? 50 times more 10 times more 2 times more 5 times more

Clarence wants to buy a new car. he finds an ad for a car that costs 27,200 dollars. suppose his local sales tax is 7%. -how much would he have to pay? -what is the cost of the car including tax? -if clarence has 29,864 saved, can he pay cash to buy the car?