Answer:
The answer to your question is x<-8, hope this helps :)
Answer:
The answer to your question is
Part A. Archimedes grades 6 1/4 tests per day
Part B. 8 19/32 days
Part C. 6 26/29 days
Step-by-step explanation:
Part A
Total time = 6 2/5 days
Number of tests = 40 tests
Process
1.- Convert the mixed fraction to improper fraction
6 2/5 = (30 + 2) / 5 = 32/5
2.- Divide 40 by 32/5
40/1 / 32/5 = (40 x 5) / (32 x 1)
= 200 / 32
Simplify
100 / 16 = 50/8 = 25/4
3.- Convert 25/4 to mixed fractions
6
4 25
1
25/4 = 6 1/4
Archimedes grade 6 1/4 tests per day
Part B
15 more tests
Total time = 32/5
Total tests = 40 + 15 = 55
Process
1.- Divide 55 by 32/5
55 / 1 / 32 /5 = (55 x 5) / (32 x 1)
= 275 / 32
2.- Convert 275/32 to a mixed fraction
8
32 275
256
19
Result 8 19/32 days
Part C
1.- Divide 55 by 7.25
50 / 7.25 = 5000 / 725
6
725 5000
- 4350
650
Result 6 650/750 = 6 26/29
Population = 135 students
Mean score = 72.3
Standard deviation of the scores = 6.5
Part (a): Students from 2SD and 3SD above the mean
2SD below and above the mean includes 95% of the population while 3SD includes 99.7% of the population.
95% of population = 0.95*135 ≈ 129 students
99.7% of population = 0.997*135 ≈ 135 students
Therefore, number of students from 2SD to 3SD above and below the bean = 135 - 129 = 6 students.
In this regard, Students between 2SD and 3SD above the mean = 6/2 = 3 students
Part (b): Students who scored between 65.8 and 72.3
The first step is to calculate Z values
That is,
Z = (mean-X)/SD
Z at 65.8 = (72.3-65.8)/6.5 = 1
Z at 72.3 = (72.3-72.3)/6.5 = 0
Second step is to find the percentages at the Z values from Z table.
That is,
Percentage of population at Z(65.8) = 0.8413 = 84.13%
Percentage of population at (Z(72.3) = 0.5 = 50%
Third step is to calculate number of students at each percentage.
That is,
At 84.13%, number of students = 0.8413*135 ≈ 114
At 50%, number of students = 0.5*135 ≈ 68
Therefore, students who scored between 65.8 and 72.3 = 114-68 = 46 students
