A card shop contains 10 birthday cards, 10 holiday cards, and 9 graduation cards. If three cards are purchased at random from the shop, what is the probability that the three cards will be of the same type?  Choose the correct choice from the following answers
A) 3/29  B) 12/58  C) 12/840  D) 7/841  E) 12/841
It doesn't matter which type of card you choose, so:   Probability of choosing 1st card: 1   Probability of choosing 2nd card of the same type: 4/29   Probability of choosing 3rd card of the same type: 3/29   Multiply and you get 12/841   Answer 12/841.
<result>E</result>
A card shop contains 10 birthday cards, 10 holiday cards, and 9 graduation cards. If three cards are purchased at random from the shop, what is the probability that the three cards will be of the same type?