SOLUTION: A box contains 20 blocks. Fifteen of the blocks are red, the rest are green. If six blocks are selected at random, how many ways can six red blocks be selected? I have tried 20P

Question 727248: A box contains 20 blocks. Fifteen of the blocks are red, the rest are green. If six blocks are selected at random, how many ways can six red blocks be selected?
I have tried 20P6 but I am not sure that is the right formula to be using. I figure some sort of probability of red vs. green needs to be included.
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
Order does NOT matter, so you do NOT use n P r (permutation), you use n C r (combination)

So there are 15 C 6 = 5005 distinct ways to pick 6 red blocks

This is out of 20 C 6 = 38760 ways total (to pick any color block and pick 6 of them)

So the probability of picking 6 red blocks is

P(6 red blocks) = (# of ways to pick 6 red blocks)/(# of ways to pick 6 blocks)

P(6 red blocks) = (15 C 6)/(20 C 6)

P(6 red blocks) = (5005)/(38760)

P(6 red blocks) = 0.12912796697627
RELATED QUESTIONS
A box contains 20 blocks. Fifteen of the blocks are red, the rest are green. If 6 blocks... (answered by ewatrrr)

A bag contains 18 blocks, 7 of which are red, 8 are blue, and the rest are green. If 7... (answered by Boreal)

There are four green blocks and four red blocks in a bag. Two blocks are selected at... (answered by stanbon)

A bag contains 12 blocks. Six are red, two are blue, and three are green, and the rest... (answered by htmentor)

A pyramid of blocks has 26 blocks at the bottom row and 2 fewer blocks each successive... (answered by Boreal)

A box contains 80 blocks, some of which are made of wood and some of which are made of... (answered by richwmiller)

There are 4 green blocks and 3 red blocks in a bag. What’s the probability of selecting (answered by Edwin McCravy)

There are 4 green blocks and 3 red blocks in a bag. What’s the probability of selecting (answered by ikleyn)

Five blocks are painted red, blue, green, yellow, and white. In how many different ways... (answered by alicealc)