ACT mathematics score for a particular year are normally distributed with a mean of 28 and a standard deviation of 2.4 points
1 answer:
Answer:
a. 0.1587
b. 0.8849
c. 0.1814
Step-by-step explanation:
a. Given that
-The probability a randomly selected score is greater than 30.4 is calculated as:
Hence, the probability of a score greater than 30.4 is 0.1587
b. Given that
The probability a randomly selected score is less than 32.8 is calculated as:
Hence, the probability that a randomly selected score is less than 32.8 is 0.8849
c. The probability that a score is between 25.6 and 32.8 is calculated as follows:
Hence, the probability is 0.1814
You might be interested in
Solution:
Let x represent a number of calling minutes. According to the problem, we want:
now, putting the similar terms together, we obtain:
this is equivalent to:
now, solving for x, we get:
then, the correct answer for the first question is:
400 minutes is the number of minutes the two plans cost the same
now, for the second question, we can replace the above value (400 minutes) into the following equation:
so that, the correct answer for the second question is:
$55 is the cost when the two plans cost the same