When are the clock hands perpendicular

Find the area of the surface obtained by rotating the curve z=4e^2y from y = 0 to y =1 about the y-axis. the area is square units

Abby is collecting rainfall data. she finds that one value of the data set is a high-value outlier. which statement must be true? abby will use a different formula for calculating the standard deviation. the outlier will increase the standard deviation of the data set. the spread of the graph of the data will not change. abby will not use the mean when calculating the standard deviation.

How many four digit even numbers can be formed from digits 1,2,3,4,5 if repetition is allowed. how can solve this using permutation formula