a) How many numbers among 1,2,3,...,1000 are not divisible by 9?

b) Dmitri has a pair of standard dice; one die is blue, and the other die is yellow. He rolls both of his dice. How many ways could the number on the blue die be larger than the number on the yellow die?

c) Hae Suk flips a penny, a nickel, and a dime. How many ways can she get at least two heads?

Guest Apr 14, 2019