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
49,997/50,000
Is the probability of not being struck by a unicycle
Answer:
So if he has 24 friends and each one got 4 then he would have 1 cars left for himself.
Step-by-step explanation:
Answer:
15Step-by-step explanation:y = family members = 7x = cos
Step-by-step explanation:
Answer:
the rate of the first cyclist: 28km/h
the rate of the 2nd cyclist 28+4= 32km/h
Step-by-step explanation:
x= the rate of the first cyclist
x+4= the rate of the 2nd cyclist
after 4 hours: + the first cyclist travels 4x (km)
+ the 2nd cyclist travels 4(x+4) (km)
because the two cyclists are 240 km apart after 4 hours
=> 4x + 4(x+4) = 240 => x= 28
i hope it's useful forr u =)))