Answer:
Mean = 78.2
Standard deviation = 5.8
Step-by-step explanation:
Mathematically z-score;
= (x-mean)/SD
From the question;
12% of test scores were above 85
Thus;
P( x > 85) = 12%
P(x > 85) = 0.12
Now let’s get the z-score that has a probability of 0.12
This can be obtained from the standard normal distribution table and it is = 1.175
Thus;
1.175 = (85 - mean)/SD
let’s call the mean a and the SD b
1.175 = (85-a)/b
1.175b = 85 - a
a = 85 - 1.175b ••••••••(i)
Secondly 8% of scores were below 70
Let’s find the z-score corresponding to this proportion;
We use the standard normal distribution table as usual;
P( x < 70) = 0.08
z-score = -1.405
Thus;
-1.405 =( 70-a)/b
-1.405b = 70-a
a = 70 + 1.405b ••••••(ii)
Equate the two a
70 + 1.405b = 85 - 1.175b
85 -70 = 1.405b + 1.175b
15 = 2.58b
b = 15/2.58
b = 5.81
a = 70 + 1.405b
a = 70 + 1.405(5.81)
a = 78.16
So mean = 78.2 and Standard deviation is 5.8
To decrease this amount by 15% we must first find out what is 15% percent.
We can do that by multiplying the decimal of 15% by 120
15% = 0.15
0.15 x 120 = 18
So 18 is 15% of 120.
Wait! that's not the answer. We are asked to decrease by 15%
So 120 - 18 = 102
Your answer is £102
Answer:
x=3
Step-by-step explanation:
Given,
1 = 1/(x-2)
Multiply both sides by (x-2),
1*(x-2) = 1/(x-2) * (x-2)
x-2 = 1
Adding 2 on both sides,
x-2+2 = 1+2
x = 3
The actual height of building is 1800 feet.
Step-by-step explanation:
Given,
Height of building in model = 3 inches
Scale used by engineer;
1 inch = 600 feet
Therefore;
Actual height of building = Height in model * Scale used
Actual height of building = 3 * 600
Actual height of building = 1800 feet
The actual height of building is 1800 feet.
We find the area of the total square which is 8in • 8in=64in^2 . Now we find the area of the small quadrilateral which is 4in•4in=16 in^2.
Now we subtract the area of the small quadrilateral from the big quadrilateral’s area 64in^2 -16in^2 leaving us with the are of 48in^2 of the figure
