Answer:
The plumber worked 50 hours, and his assistant worked 25 hours.
Step-by-step explanation:
Since a plumber and his assistant work together to replace the pipes in an old house, and the plumber charges $ 30 an hour for his own labor and $ 20 an hour for his assistant's labor, and the plumber works twice as long as his assistant on this job, and the labor charge on the final bill is $ 2000, to determine how long did the plumber and his assistant work on this job the following calculation must be performed:
40 x 30 + 20 x 20 = 1200 + 400 = 1600
50 x 30 + 25 x 20 = 1500 + 500 = 2000
Therefore, the plumber worked 50 hours, and his assistant worked 25 hours.
Answer:
b. 4x-8
Step-by-step explanation:
1/2 x(8x-16)
= 1/2(8x) - 1/2 (16)
=4x - 8
Hope this helped
Subtract original amount from new amount:
84 - 39 = 45
He bought 45 books.
Step-by-step explanation:
Given
<span>n = 5
The formula for the confidence interval (CI) is
CI = m ± z*d/sqrt(n)
where
CI = confidence interval
m = mean
z = z value in standard normal table for desired confidence
n = number of samples
Since we want a 95% confidence interval, we need to divide that in half to get
95/2 = 47.5
Looking up 0.475 in a standard normal table gives us a z value of 1.96
Since we want the margin of error to be ± 0.0001, we want the expression ± z*d/sqrt(n) to also be ± 0.0001. And to simplify things, we can omit the ± and use the formula
0.0001 = z*d/sqrt(n)
Substitute the value z that we looked up, and get
0.0001 = 1.96*d/sqrt(n)
Substitute the standard deviation that we were given and
0.0001 = 1.96*0.001/sqrt(n)
0.0001 = 0.00196/sqrt(n)
Solve for n
0.0001*sqrt(n) = 0.00196
sqrt(n) = 19.6
n = 4.427188724
Since you can't have a fractional value for n, then n should be at least 5 for a 95% confidence interval that the measured mean is within 0.0001 grams of the correct mass.</span>
