Math

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Can someone help me verify if this is correct?

Gasoline usage for compact cars in Canada is a normal distribution with a mean of 33.3 km/l and with standard deviation of 7.3 km/L. Round your answers to one decimal place.

a) What percentage of compact cars obtains 20km/L or LESS?

z= x-mean/standard deviation
= 20-33.3/7.3
= 1.82 Km/L

(find percent through z-score table)

which becomes 0.0344 x 100
= 3.4 %

b) What percentage of compact cars obtains MORE than 40 km/L

z=40-33.3/7.3
= 0.92 km/L = 0.8212
= 1 - 0.8212
= 0.1788 x 100
= 17.9%

Question is, for question b, is it 1-0.8212 or 100-0.8212?

  • Math -

    a) Z = -1.82 ≠ 1.82 Km/L

    Otherwise it is correct.

    b) Z = .92 (not km/L)

    Don't need to subtract from one (which is correct of the two), if you use column for proportion in smaller area in the table.

    Final answer correct.

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