Answer:
18
Step-by-step explanation:
Khan Academy
The first answer is 40 second 65 third 56 and then fourth 90
Answer: The total number of student in the school = 240.
Step-by-step explanation:
Let x be the total number of students in the school.
Given: 35% of the students at Charles drew middle school are 6th graders.
i.e. Number of sixth graders = 35% of x = 0.35x [35% = 0.35]
Since there are 84 sixth graders in the school,
So 
Divide both sides by 0.35, we get

Hence, the total number of student in the school = 240.
Answer:
b. 2.28%.
Step-by-step explanation:
Mean temperatue (μ) = 1000°F
Standard Deviation (σ) = 50
°F
For any temperature value, X, the z-score is given by:
For X= 900°F

A z-score of -2.0 corresponds to the 2.28-th percentile of a normal distribution. Therefore, the probability that X<900 is:

8x10^5 = 800,000
times 800,000 by 0.5 (or just half it) would equal 400,000, which is translated to 4x10^5