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:
The volume can be found by multiplying these two numbers, which is
65/4 x 1/2
65/8 units^3
Let me know if this helps!
Answer:
x≥9
Step-by-step explanation:
Pretend the Less than or equal to sign is just an equals sign
-7x+7=-56 Solve:
-7x=-56-7
-7x=-63
For the last step, if you divide a negative number, the Sign switches. So not the sign is greater than or equal to.
x>=9
20miles increased by 30%=new mileage added
20x.3= 6
6 miles more than his previous distance so...
6+20= 26
NOTE you can also use 1.3 instead of .3 as the percent to get the answer with out addition.
Answer:2/16
Step-by-step explanation:
