Answer:
C, Length = 39.4 cm; width = 7.9 cm
Step-by-step explanation:
The permimeter of a rectangle is 2 times the width + 2 times the length or 2(l + w)
The length is 4 times w plus 7.8.
So: 2w+2(4w+7.8)=94.6
= 2w+8w+15.6=94.6 (Factor out the brackets)
= 10w+15.6=94.6 (Combine like terms)
= 10w=79 (Subtract 15.6 from both sides)
= w=7.9 (Divide both by 10).
So, the width is 7.9 cm and the length is 39.4 cm (4 * 7.9 + 7.8)
Answer:
It is 49. You will know it is right down here:
Step-by-step explanation:
1323 when factorised = 3 *3*3*7*7
Therefore it is to be divided by 7*7 = 49
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Answer:
Step-by-step explanation:
We want to determine a 95% confidence interval for the mean mean test score of students.
Number of sample, n = 25
Mean, u = 81.5
Standard deviation, s = 10.2
For a confidence level of 95%, the corresponding z value is 1.96. This is determined from the normal distribution table.
We will apply the formula
Confidence interval
= mean ± z score ×standard deviation/√n
It becomes
81.5 ± 1.96 × 10.2/√25
= 81.5 ± 1.96/× 2.04
= 81.5 ± 3.9984
The lower end of the confidence interval is 81.5 - 3.9984 =77.5
The upper end of the confidence interval is 81.5 + 3.9984 = 85.5
Therefore, with 95% confidence interval, the mean test score of students is between 77.5 and 85.5
Answer:
0.0359
Step-by-step explanation:
Data provided:
mean values of three independent times are 15, 30, and 20 minutes
the standard deviations are 2, 1, and 1.6 minutes
Now,
New Mean = 15 + 30 + 25 = 65
Variance = ( standard deviation )²
or
Variance = 2² + 1² + 1.6² = 7.56
therefore,
Standard deviation = √variance
or
Standard deviation = 2.75
Thus,
Z-value = 
or
Z-value = - 1.81
from the Z-table
the Probability of Z ≤ -1.81 = 0.0359
