Please help im stuck and completely lost

Which of the following answers is 5/25 simplified? 1/5 5/5 2/5 1/25

Describe the 2 algebraic methods you can use to find the zeros of the function f(t)=-16t^2+400.

The circumference of a redwood tree trunk is 20π ft, and it is 100 ft tall. what is the approximate volume of the redwood tree trunk? 1,000π ft3 10,000π ft3 4,000π ft3 40,000π ft3