probability question:
customers at a store independently decide whether to pay by credit card or with cash. Suppose the probability is 70% that a customer pays by credit card. Find the probability
a) 3 out of 5 customers pay by credit card
b) the 5th customer is the 3rd one to pay by credit card.

Question

probability question:
customers at a store independently decide whether to pay by credit card or with cash. Suppose the probability is 70% that a customer pays by credit card. Find the probability 
a) 3 out of 5 customers pay by credit card
b) the 5th customer is the 3rd one to pay by credit card.

shubhamsrg · Answer

Can you notice these can be treated as bernoulli trials ?

anonymous · Answer

we did not learn that in class.....D;

anonymous · Answer

but thank you for the hint! Now i can find out part a by using the bernoulli trials you just mentioned.

shubhamsrg · Answer

(Y)

anonymous · Answer

but what should i do for part b though?

shubhamsrg · Answer

similar approach, this time you have 2 people out of first 4 paying via credit card as you know the 5th one is paying through credit card only.

anonymous · Answer

so i assume there are four people and only two of them paid by credit card multiply the possibility of 5th customer who will pay by credit card?

anonymous · Answer

i think i got it. thank you so much

shubhamsrg · Answer

right.
yw (: