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:
168 pages
Step-by-step explanation:
each night you read 28 pages, so 6 nights you have to read for 28x6=168 pages.
The quantity demanded would increase due to the cheaper price people would want to take advantage and buy it when it was on sale. There is not enough information to determine whether the supply or demand would maintain so D is your answer.
X^2 - 9x + 18
factors of 18: 1*18, 2*9, 3*6,
the sums of the factors: 19, 11, 9
the positive 18 tells us both factors have the same sign, the negative 9 tells us they are both negative
(x - 3)(x - 6)
Answer:
It is +2 or since (+2)*(+2 ) gives. If you think that it would be (-2) also then you are wrong because root of a positive rational number is always positive number.
Step-by-step explanation:
Let the square root of four be ‘k’.
Then we have
(4)^1/2=k
(Squaring both sides)
4=(k)^2
=>(k)^2–4=0
=>(k)^2-(2)^2=0
=>[k+2][k-2]=0 {since (a)^2-(b)^2=(a+b)(a-b)}
if product of two numbers is 0 then either of one must be zero.
If k+2=0 then k=-2
If k-2=0 then k=2
From here we got two answers but -2 should be omitted because when we square an equation we add “root extra”which means that when we square an equation one root is added.
