Abag contains 4 red marbles and 5 blue marbles. if two marbles are chosen at random, one at a time and without replacement, what is the probability of getting two red marbles?

Suppose a laboratory has a 30 g sample of polonium-210. the half-life of polonium-210 is about 138 days how many half-lives of polonium-210 occur in 1104 days? how much polonium is in the sample 1104 days later? 9; 0.06 g 8; 0.12 g 8; 2,070 g