last saturday micheal spent 2/6 of an hour cleaning the hamster cage 3/12 of an hour walking the dog around the block and 5/60 of an hour feeding the bird what part of and hour did micheal spend taking care of his pets

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%)