Chen's pocket holds 10 coins: 3 quarters, 4 dimes, 1 nickle, and 2 pennies. What are the chances that he first randomly pulls out a quarter and then, without putting the quarter back in, pulls out a penny at random?

All the outcomes are 10 (possibilities)

To pull a quarter (total 3), its probability = 3/10 or 0.3

Now without putting the quarter back, the remaining total is now 9 (because one quarter was pulled out) so the probability of getting a penny is 2/9

But this is a conditional probability a) 1st pull a quarter & 2nd pull a penny

So the total probability is 3/10 x 2/9 = 6/90 = 1/15 = 0.067