The general equation of an arithmetic series is 
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Answer:
30 first graders
Step-by-step explanation:
Total number of students in school=40
Percentage of first graders =75%
No.of first graders = (75÷100) ×40
=0.75×40=30 first graders.
Answer:
Step-by-step explanation:
Since the length of time taken on the SAT for a group of students is normally distributed, we would apply the formula for normal distribution which is expressed as
z = (x - u)/s
Where
x = length of time
u = mean time
s = standard deviation
From the information given,
u = 2.5 hours
s = 0.25 hours
We want to find the probability that the sample mean is between two hours and three hours.. It is expressed as
P(2 lesser than or equal to x lesser than or equal to 3)
For x = 2,
z = (2 - 2.5)/0.25 = - 2
Looking at the normal distribution table, the probability corresponding to the z score is 0.02275
For x = 3,
z = (3 - 2.5)/0.25 = 2
Looking at the normal distribution table, the probability corresponding to the z score is 0.97725
P(2 lesser than or equal to x lesser than or equal to 3)
= 0.97725 - 0.02275 = 0.9545
30 * 1/5 = 6 so 6 have a cell phone
1/2 * 6 = 3 so 3 have a cellphone and social media
195 divide by 2 1/2
195 divide 5/2 (copy dot flip)
195 * 2/5
78 loads of laundry
19.99 divide by 78
.256
.26
he is paying 26 cents for each load
