Answer:

Standard error of mean = 689
Step-by-step explanation:
We are given the following information in the question:
Mean, μ = $28,520
Standard Deviation, σ = $5600
Mean of sampling distribution =

As per Central Limit Theorem, if the sample size is large enough, then the sampling distribution of the sample means follow approximately a normal distribution.
Sample size, n = 66
Since the sample size is large, we can use normal distribution for approximation.
Standard error of mean =

Answer:
216 boys
Step-by-step explanation:
450 students: 20% girls, 80% boys
450*20%=90 girls
450*80%=360 boys
Students having mobile phones: 40% (OF THE 90) girls, 60% (OF THE 360) boys
90*40%=36 girls
360*60%=216 boys
[We honestly don't need to care about the girls without mobile phones as they are only asking how many boys have mobile phones]
Answer:
hi buddy
Step-by-step explanation:
1 50
2 5 %
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12/15
Divide 12 by 15 and then you should get 0.8
0.8 is obviously equal to 8/10ths or 80%
Hope this helps :)