Bunuel
A store had 10 loaves of bread, out of which 7 were baguettes. If the store sold 6 loaves of bread, what is the probability that the store sold exactly 4 baguettes out of these 6 loaves? (Assume that every loaf has an equal chance of selling)
A. \(\frac{2}{5}\)
B. \(\frac{3}{5}\)
C. \(\frac{2}{3}\)
D. \(\frac{1}{2}\)
E. \(\frac{4}{7}\)
I have different approach - to use probability theory.
Let's get a product of all possible descreate probabilities.
What is probability to get 1 baguette? It's 7/10. If we get 1 baguette and want to get one more baguette, then probability to get two baguettes is product of 7/10 * 6/9.
Move on and on, eventually we will get the following:
\(7/10 * 6/9 * 5/8 * 4/7 * 3/6 * 2/5 = 1/30\)
It's a probability to get 4 baguettes and 2 loaves of other kind. But probability that we got works only if we get loaves in exactly following order: baguette + baguette + baguette + baguette + nonbaguette + nonbaguette
But there can be another order. In order to count a number of all possible orders we have to find \(6!/4!*2! = 15\)
So, we have to summ gotten probability 15 times. It means \(1/30 * 15 = 1/2\)
So the sought probability is \(1/2\)
This is the approach I initially used before guessing around the 2 min mark. Can you explain why you are multiplying 6!/4! by 2!?