Question

A bag contains 4 white and 6 black marbles. 28 students each reach in, select a marble, record its color, then replace the marble.
a. what is the probably that exactly 10 select white marbles?
b. What is the probability that no more than 10 students select white marbles?

Answer 1

@rebeccaskell94

Answer 2

yes?

Answer 3

hey @tiaph, sorry about all the probability Q's, but im studying for a retake

Answer 4

(a) Exactly 10 students select white marbles. (4/10)^10 * (6/10)^18

(b) No more than 10 students select white marbles.
It is a long way, im trying to find a shorter method.

Answer 5

whats b?

Answer 6

Part b of your question?

Answer 7

yeah, and could you explain a. a little more?

Answer 8

diagram, perhaps?

Answer 9

okay a first then.

Exactly 10 students choose white marbles.
The probability of choosing white marble is 4/10 ( since 4 white marbles out of 10 total).
So for 10 students to choose white marble it will be just 4/10 * 4/10 * 4/10 * 4/10.... multiply 10 times, thus (4/10) ^10

Answer 10

ohhh... okay, i understand a

Answer 11

Unfortunately there is no diagram that can help, because it is big in numbers, drawing a tree diagram would be too waste of an effort.

As for B. There is not shorter way to do it, you just have to count.

No more than 10 students select white marbles. means 10 or less.

Thus u need to add the probability that 1 student select white marble, and 2 student select white marble, and 3 student and 4 so on and so forth until u hit 10..

Answer 12

so 4/10^2 divide by 6/10^18 ?

Answer 13

So it will be something like this....

(4/10)(6/10)^27 + (4/10)^2 (6/10) ^26 + (4/10)^3 (6/10)^25............until (4/10)^10 (6/10)^18

Answer 14

to get prob of exactly 10?

Answer 15

can this be solved with combinations?