Answer:
0.36427
Step-by-step explanation:
Mean = λ = 18 messages per hour
P(X = x) = (e^-λ)(λ⁻ˣ)/x!
P(X ≤ x) = Σ (e^-λ)(λ⁻ˣ)/x! (Summation From 0 to x)
But the probability required is that the messages thay come in an hour is between 15 and 20, that is, P(15 < X < 20)
P(15 < X < 20) = P(X < 20) - P(X ≤ 15)
These probabilities will be evaluated using a cumulative frequency calculator.
P(X < 20) = 0.65092
P(X ≤ 15) = poissoncdf(18, 15) = 0.28665
P(15 < X < 20) = P(X < 20) - P(X ≤ 15) = 0.65092 - 0.28665 = 0.36427.
You can use the Poisson distribution calculator here
https://stattrek.com/online-calculator/poisson.aspx
They each get half a slice of pizza
Jace bought 4 cookies and 2 brownies from the bakery.
Let x represent the number of cookies and y represent the number of brownies.
Since he bought $9 worth of cookies and brownies. Each cookie costs $0.75 and each brownie costs $3. hence:
0.75x + 3y = 9 (1)
Also, he bought twice as many cookies as brownies, hence:
x = 2y
x - 2y = 0 (2)
Solving equation 1 and 2 simultaneously gives x = 4, y = 2
Hence Jace bought 4 cookies and 2 brownies from the bakery.
