12 more boys than girls
ratio of boys to girls = 7:5
thus 2/12 is difference between boys and girls = 12
total students = 12 ÷ 2/12 = 72
Answer:
The probability that at most 38 of the 60 relays are from supplier A is P(X≤38)=0.3409.
Step-by-step explanation:
We can model this question with a binomial distribution random variable.
The sample size is n=60.
The probability that the relay come from supplier A is p=2/3 for any relay.
If we use a normal aproximation, we have the mean and standard deviation:

The probability that at most 38 of the 60 relays are from supplier A is P(X≤38)=0.3409:

47.C
48.B
49.???
50.A
sorry doing something couldn't solve 49 right now