Please solve pre calculus i am cruing

The perimeter of a quarter circle is 14.28 miles. what is the quarter circle's radius?

Compute the standard deviation of the following set of data to the nearest whole number. 10, 10, 15, 20, 25

The table below shows the approximate masses of a dust particle and a grain of pollen. dust particle 0.000000778 g grain of pollen 0.00000000155 g the mass of a dust particle can be estimated and written in the form a × 10^b, where a = 8 and b = the mass of a grain of pollen can be estimated and written in the form a × 10^b, where a = 2 and b = based on the estimates, the mass of a dust particle is approximately blank times larger than the mass of a grain of pollen.