The number of hours a certain type of battery will last is distributed normally with a mean of 500 minutes. The
standard deviation is 50 minutes. Out of 240 batteries
tested, how many batteries would you expect to still be
working after 580 minutes?

Can somebody help me with this question?

Christina can paint 420 square feet in 105 minutes. which unit rate describes the scenario?

Circle d circumscribes abc and abe. which statements about the triangles are true? statement i: the perpendicular bisectors of abc intersect at the same point as those of abe. statement ii: the distance from c to d is the same as the distance from d to e. statement iii: bisects cde. statement iv: the angle bisectors of abc intersect at the same point as those of abe. a. i only b. i and ii c. ii and iv d. i and iii e. iii and iv

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)?