The circumference of the outside of a ring is 66 mm, and it has an outer diameter of 21 mm. If the circumference of the inside of the ring is 50 mm, what is the inner diameter of the ring?

Write and solve a real word problem that involves determining distance on a coordinate plane

Write two point-slope equations for the line passing through the points (6, 5) and (3, 1)

In a test for esp (extrasensory perception), a subject is told that cards only the experimenter can see contain either a star, a circle, a wave, or a square. as the experimenter looks at each of 20 cards in turn, the subject names the shape on the card. a subject who is just guessing has probability 0.25 of guessing correctly on each card. a. the count of correct guesses in 20 cards has a binomial distribution. what are n and p? b. what is the mean number of correct guesses in 20 cards for subjects who are just guessing? c. what is the probability of exactly 5 correct guesses in 20 cards if a subject is just guessing?