What shape is created by the rotation and what is the approximate circumference of the base?
Circumference of a circle: C = 2tr
O a cone with a base circumference of about 25 units
O a cone with a base circumference of about 50 units
O a cylinder with a circumference of about 25 units.
O a cylinder with a circumference of about 50 units

Select all the correct answers. what is 221,000,000,000,000,000,000 expressed in scientific notation?

The ph level of a blueberry is 3.1 what is the hydrogen-ion concentration [h+] for the blueberry

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.