Answer:
2?
Step-by-step explanation:
Sally paints at a rate of 1/7th room / hour
Steve paints at a rate of 1/6th room / hour
If they both painted together, they would paint 1/7 + 1/6 = 13/42 room/hour
so to paint the whole room, it would take 1/(13/42) = 42/13 =
<u>
3.23 hours (3 significant figures)</u>
Answer:
(a) The probability of having exactly four arrivals during a particular hour is 0.1754.
(b) The probability that at least 3 people arriving during a particular hour is 0.7350.
(c) The expected arrivals in a 45 minute period (0.75 hours) is 3.75 arrivals.
Step-by-step explanation:
(a) If the arrivals can be modeled by a Poisson process, with λ = 5/hr, the probability of having exactly four arrivals during a particular hour is:

The probability of having exactly four arrivals during a particular hour is 0.1754.
(b) The probability that at least 3 people arriving during a particular hour can be written as

Using

We get

The probability that at least 3 people arriving during a particular hour is 0.7350.
(c) The expected arrivals in a 45 minute period (0.75 hours) is

36-39/12-5
31-39/12
31-3.25
27.75