Solve each equation by taking square roots NEED THIS ASAP

Which number produces a rationale number when multiplied by 1/5

Assume that y varies inversely with x. if y=1.6 when x=0.5 find x when y=3.2 acellus answer

Astudent must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of b. devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a b in the course? ( assuming the highest grade is 100%)