1.5:2.5::4.5:a find the value of "a" if the given ratios are in inverse proportion

Average acceleration: i have no idea how to do this.

Assume that the weights of quarters are normally distributed with a mean of 5.67 g and a standard deviation 0.070 g. a vending machine will only accept coins weighing between 5.48 g and 5.82 g. what percentage of legal quarters will be rejected? round your answer to two decimal places.

65% of students in your school participate in at least one after school activity. if there are 980 students in you school, how many do not participate in an after school activity?