Combinations

[quaidy4]

A bag contains 6 white balls and 5 black balls. A child reaches into the bag and pulls out a handful of 4 balls, what is the probability that the child selects 4 balls of the same colour.

I think you do choose 4 of 6 white balls and choose 4 of 5 black balls, do the combination formula and then times your two answers together. Then you take 11 factorial (since the total number of balls is 11) divided by 8 factorial (since there are 8 balls) and minus 11-8 which gives you 3. Figure that all out and then divide.

 

[saravananbs]

from 11 balls child is going to select 4 balls, so its possiblity is 11C4.

but the condition is all should be in same color=child can select 4 white or child can select 4 black balls.

possibility of 4 white ball is 6C4 and possibility of 4 black is 5C4.

probability is (6C4+5C4)/11C4. where nCr=n!/(r!(n-r)!)

 

[quaidy4]

thank you!