45 children attend a preschool. the number of 2 year olds is one half the number of 3 year olds. the number of 4 year olds is the same as the number of 3 year olds.

a. how many 2 year olds attend preschool
b. how many 3 year olds attend preschool
c. how many 4 year olds attend preschool

Yesterday, george drank 1 small bottle and 2 large bottles, for a total of 1,372 grams. the day before , he drank 1 small bottle and 1 large bottle, for the total of 858 grams. how many grams does each bottle hold?

Events a and b are independent. the probability of a occurring is 2/5. the probability of b occurring is 1/4. what is p(a and b)?

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%)