Well, these are quite simple really, especially 1,2,3 and 4. If you read the questions carefully, you can understand it well. You don’t need to know the answer, you just need to understand
The solution (400, 3, 200) is the answer to a system of equations which has three variables. Respectively, this system is expected to have three equations because it has three unknowns. So for example if your unknowns are x, y and z, then the answers will be x=400, y=3, and z=200.
Answer:
a) 0.7063; b) 0.0228; c) 0.2709
Step-by-step explanation:
We use z scores for these problems. The formula for a z sore is

For part a,
We want P(5 ≤ X ≤ 11):
z = (5-9.6)/2.3 = -4.6/2.3 = -2
z = (11-9.6)/2.3 = 1.4/2.3 = 0.61
The area under the curve to the left of z = -2 is 0.0228. The area under the curve to the left of z = 0.61 is 0.7291. This makes the area between them
0.7291 - 0.0228 = 0.7063
For part b,
We want P(X ≤ 5):
z = (5-9.6)/2.3 = -4.6/2.3 = -2
The area under the curve to the left of z = -2 is 0.0228.
For part c,
We want P(X > 11):
z = (11-9.6)/2.3 = 1.4/2.3 = 0.61
The area under the curve to the left of z = 0.61 is 0.7291. However, we want the area to the right; this means we subtract from 1:
1-0.7291 = 0.2709
Yep! Because it is always a pattern of 0 to 5