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A new car that is a gas- and electric-powered hybrid has recently hit the market

ID: 3152035 • Letter: A

Question

A new car that is a gas- and electric-powered hybrid has recently hit the market. The distance traveled on 1 gallon of fuel is normally distributed with a mean of 50 miles and a standard deviation of 8 miles. Find the probability of the following events A. The car travels more than 55 miles per gallon Probability = .2676 B. The car travels less than 43 miles per gallon Probability = .1922 C. The car travels between 45 and 55 miles per gallon Probability = -73237-26763 than 55 miles per gallon Probability -73237-26763

Explanation / Answer

A)

We first get the z score for the critical value. As z = (x - u) / s, then as          
          
x = critical value =    55      
u = mean =    50      
          
s = standard deviation =    8      
          
Thus,          
          
z = (x - u) / s =    0.625      
          
Thus, using a table/technology, the right tailed area of this is          
          
P(z >   0.625   ) =    0.265985529 [ANSWER]

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b)

We first get the z score for the critical value. As z = (x - u) / s, then as          
          
x = critical value =    43      
u = mean =    50      
          
s = standard deviation =    8      
          
Thus,          
          
z = (x - u) / s =    -0.875      
          
Thus, using a table/technology, the left tailed area of this is          
          
P(z <   -0.875   ) =    0.190786953 [ANSWER]

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c)

We first get the z score for the two values. As z = (x - u) / s, then as          
x1 = lower bound =    45      
x2 = upper bound =    55      
u = mean =    50      
          
s = standard deviation =    8      
          
Thus, the two z scores are          
          
z1 = lower z score = (x1 - u)/s =    -0.625      
z2 = upper z score = (x2 - u) / s =    0.625      
          
Using table/technology, the left tailed areas between these z scores is          
          
P(z < z1) =    0.265985529      
P(z < z2) =    0.734014471      
          
Thus, the area between them, by subtracting these areas, is          
          
P(z1 < z < z2) =    0.468028942   [ANSWER]  

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