Answer:
D.
40 x 6.4 = 256
256/128=2 so 2 gallons.
Step-by-step explanation:
Answer: 271
Step-by-step explanation:
The formula we use to find the sample size is given by :-

, where
is the two-tailed z-value for significance level of 
p = prior estimation of the proportion
E = Margin of error.
If prior estimation of the proportion is unknown, then we take p= 0.5 , the formula becomes


Given : Margin of error : E= 0.05
Confidence level = 90%
Significance level 
Using z-value table , Two-tailed z-value for significance level of 

Then, the required sample size would be :

Simplify,

Hence, the required minimum sample size =271
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Slope intercept form: y = mx + b
m = slope and b = y-intercept
The equation is: y = -3x + 6
The m value for this is -3, so the line has a slope of -3. If y = 1/3x - 8 was parallel to y = -3x + 6 then they would have the same slope, which they do not. So they aren't parallel.
The find the slope of a perpendicular line, take the negative reciprocal of the slope of y = -3x + 6. The negative reciprocal of -3 is 1/3. y = 1/3x - 8 has a slope of 1/3, so they are perpendicular to each other.