Question

There are 10 boxes in a grab bag boxes are identical except for its at 7 of them contain $20 bills a contest winner gets too pick two boxes from the grab bag which is the probability of getting two $20 bills

Answer 1

well if you draw 1 boxes u have 7/10 chances to get a 20$ box and the second draw has a chance of 6/9 thats if u got a 20$ on the first box if not it's 7/9 so the anwser would be 7/15 because u have to add the remaining boxes to the overall total also

Answer 2

46.67% probability of getting two $20 bills

Explanation:

A probability is the number of desired outcomes divided by the number of total outcomes.

The order in which the boxes are chosen is not important, so the combinations formula is used to solve this question.

Combinations formula:

`C_(n,x)` is the number of different combinations of x objects from a set of n elements, given by the following formula.

`C_(n,x) = (n!)/(x!(n-x)!)`

Desired outcomes

There are 7 boxes with $20 bills.

We want to grab two of them. So

`D = C_(7,2) = (7!)/(2!(7-2)!) = 21`

Total outcomes

2 boxes, from a set of 10. So

`T = C_(10,2) = (10!)/(2!(10-2)!) = 45`

Probability:

`P = (D)/(T) = (21)/(45) = 0.4667`

46.67% probability of getting two $20 bills