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(15 points) The \"fuel\" efficiency in an electric car is not measured in miles/

ID: 3364872 • Letter: #

Question

(15 points) The "fuel" efficiency in an electric car is not measured in miles/gallon, but rather in Watt-hours/mile (Wh/mile). Calculate the average and standard deviation of the following set of fuel efficiencies for a car. All values have the units Wh/mile. The various efficiencies represent the driving technique. 256, 333, 375, 324, 294, 288, 301, 311, 312, 250, 222 (5 points) If the driver of a car with a 75 KWh battery adjusts his/her technique to the average of the above values, how far can the car go? 279 Wh/mile, 190 200 miles 297 Wh/mile, 0.29 0.30 miles 290 Wh/mile, 290- 300 kilometers 297 Wh/mile, 250 260 miles

Explanation / Answer

Solution

Let x1, x2, ……. , x11 be the given fuel efficiency figures (in Wh/mile, i.e., Watt hours per mile)

Then,

Average efficiency = Xbar = (1/11) [i = 1, 11](xi) = 3266/11 = 296.9091 ANSWER 1

Variance = (1/11)[i = 1, 11](xi - Xbar)2 = (1/11)[i = 1, 11](xi2) – (Xbar)2

= (987856/11) – (296.9091)2 = 1650.083

Standard Deviation = sqrt(Variance) = 40.621 ANSWER 2

Given battery capacity as 75 KWh which is adjusted to the average fuel efficiency as obtained above, the distance the car can travel = (75 x 1000)/296.9091 = 252.6026.[note that 1 KW = 1000W]

Thus, the correct answer option is: last option:297 Wh/mile, 250 – 260 miles. ANSWER 3