## anonymous one year ago An urn contains seven red balls, seven white balls, and seven blue balls, and sample of five balls is drawn at random without replacement. Compute the probability that all of the balls in the sample are the same color. (Round your answer to four decimal places.)

1. anonymous

I have half of the answer. C (21,5) = 20,349 do I multiply by 3? i also need to use C (7,5) = 21 I thought the answer was $\frac{ 5 \times 21 }{20,349}\approx0.0051$ But it is wrong

2. anonymous

all of the same color means "all red OR all white OR all blue"

3. anonymous

so $3\times \frac{\binom{7}{5}}{\binom{21}{5}}$

4. anonymous

oh yeah sorry i didn't read carefully YES multiply by 3

5. campbell_st

permutation problem rather than a combination problem since the balls aren't replaced

6. anonymous

?

7. anonymous

you get the same answer no matter which way you go it

8. anonymous

$\frac{7\times 6\times 5\times 4\times 3}{21\times 20\times 19\times 18\times 16}$same as $\frac{\binom{7}{5}}{\binom{21}{2}}$

9. anonymous

thank you I will calculate right now

10. anonymous

11. anonymous

I got 0.3999 and it was wrong. :_(

12. anonymous

I got it!!! =0.0031

13. anonymous

thank you for all your help Satellite73