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:
1 hour
Step-by-step explanation:
no explanation its common sense lol
We have to trade 5 bunnies for a donkey.
Solution:
To calculate how many bunnies could be exchanged for a donkey, we have to multiply the exchange rates of each animal/bird.
One bunny = 3/4 chickens (0.75 chicken),
One chicken = 2/5 pigs (0.4 pigs)
One pig = 2/3 donkeys (0.67 donkeys).
On multiplying all of the above rates we get,
0.75*0.4*0.67=0.2
Since we now know a bunnies worth is 0.2 donkey
Therefore, (1/0.2=5) 5 bunnies to trade for a donkey.
I believe the answer is A because the square root of 10 root 3 is approximately 17.32.
