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
Answer:
x^0 y^-3 / x^2 y^-1
= 1 / x^2 y^-1 (y^3) ...because x^0 = 1 and [(y^-1) (y^3)] = y^2
= 1/(x^2 y^2)
Answer:
4. 158
Step-by-step explanation:
First let's make things a little simpler and put these arcs in terms of x. We know that the degree measure around the outside of a circle, regardless of its size, is 360. So let's say that arc BC is x. That means that arc BDC is 360 - x. This is because arc BC + arc BDC = 360. Substituting in our x's we have:
x + 360 - x = 360 and
360 = 360. (That's just the proof that putting in our x's as we did does in fact work!)
Following the formula then, we have
and

Multiply both sides by 2 to get rid of the fraction and get
44 = 360 - 2x
Subtract 360 rom both sides to get
-316 = -2x
Divide both sides by -2 to get that x = 158
Since we are looking for arc BC and we designated arc BC as our x, that means that arc BC = 158.
Answer:
24 is correct answer
Step-by-step explanation:
its a 5:15 ratio, you are finding 8:x
8/5=1.6-> 1.6 x a5 = 24