A. Let x = cheese and
y = chocolate
2x + y = 25
x + y = 20
B. Subtract the second equation from the first.
2x + y = 25
-(x + y = 20)
-—————
x = 5
Plug 5 back in to the second equation and solve for y.
x + y = 20
5 + y = 20
Subtract 5 from both sides.
y = 15
5 cheese and 15 chocolate
Used elimination method because coefficients on the y values were both 1 so it was easy to subtract the equations and eliminate the y variable.
The square root of 5 is 2.23 so it would be closer to 2
The probability would be 0.9738.
We first find the z-score for each end of this interval:
z = (x-μ)/(σ/√n) = (100-110)/(18/√49) = -10/(18/7) = -3.89
z = (x-μ)/(σ/√n) = (115-110)/(18/√49) = 5/(18/7) = 1.94
Using a z-table (http://www.z-table.com) we see that the probability that a score is less than the first z-score is 0. The probability under the curve to the left of, less than, the second z-score is 0.9738. Subtracting these we find the area between them:
0.9738 - 0 = 0.9738.