4. the salaries of a school cook, custodian, and bus driver are in the ratio 2: 4: 3. if their
combined monthly salaries for november total $8,280, what is the monthly salary for each
person?

Step-by-step explanation:

There are a total of 2+4+3 = 9 "ratio units", so each one is worth ...

  $8,280/9 = $920

Multiplying the ratio by $920, we get ...

  cook : custodian : bus driver = $920 × (2 : 4 : 3) = $1840 : $3680 : $2760

Option C

Step-by-step explanation:

Let X be a discrete random variable that counts the number of siblings a randomly selected student has. Then the expected value of X is defined as:

Where is the probability that a randomly selected student has siblings

With

So in this case we know that

#of siblings 0        1        2        3        4         5

probability 0.20 0.65 0.08  0.04  0.02  0.01

Therefore:

The answer is the option C.