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# When Mark fills his car with regular gasoline, he gets 20 miles/gallon

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Math Expert
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When Mark fills his car with regular gasoline, he gets 20 miles/gallon  [#permalink]

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21 Nov 2019, 01:20
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Difficulty:

55% (hard)

Question Stats:

57% (01:46) correct 43% (02:14) wrong based on 23 sessions

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When Mark fills his car with regular gasoline, he gets 20 miles/gallon. When he fills his car with premium gasoline, he gets 25 miles/gallon. If the price of regular gasoline is \$4.00 per gallon and the price of premium gas is \$6.25 per gallon, then the cost efficiency of regular gasoline, in miles/dollar, is what percent greater than the cost efficiency of premium gasoline?

(A) 4%
(B) 10%
(C) 20%
(D) 25%
(E) 50%

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Re: When Mark fills his car with regular gasoline, he gets 20 miles/gallon  [#permalink]

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21 Nov 2019, 01:46
Bunuel wrote:
When Mark fills his car with regular gasoline, he gets 20 miles/gallon. When he fills his car with premium gasoline, he gets 25 miles/gallon. If the price of regular gasoline is \$4.00 per gallon and the price of premium gas is \$6.25 per gallon, then the cost efficiency of regular gasoline, in miles/dollar, is what percent greater than the cost efficiency of premium gasoline?

(A) 4%
(B) 10%
(C) 20%
(D) 25%
(E) 50%

Regular gasoline, Cost of efficiency is per mile travel cost: 4/20= 0.2 \$ per mile
Premium gasoline, Cost of efficiency is per mile travel cost: 6.25/25= 0.25 \$ per mile

%= {(0.25 - 0.2)/0.20} * 100= 25%

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Re: When Mark fills his car with regular gasoline, he gets 20 miles/gallon  [#permalink]

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24 Nov 2019, 19:07
Bunuel wrote:
When Mark fills his car with regular gasoline, he gets 20 miles/gallon. When he fills his car with premium gasoline, he gets 25 miles/gallon. If the price of regular gasoline is \$4.00 per gallon and the price of premium gas is \$6.25 per gallon, then the cost efficiency of regular gasoline, in miles/dollar, is what percent greater than the cost efficiency of premium gasoline?

(A) 4%
(B) 10%
(C) 20%
(D) 25%
(E) 50%

We can create the equation:

(20/4 - 25/6.25)/(25/6.25) x 100

(5 - 4)/4 x 100

1/4 x 100 = 25

Alternate Solution:

Let’s calculate the cost of driving 100 miles using each type of gasoline.

Using regular gasoline, he would need 100/20 = 5 gallons, and this would cost him 5 * 4 = 20 dollars. Thus, the cost efficiency of regular gasoline is 100/20 = 5 miles/dollar.

Using premium gasoline, he would need 100/25 = 4 gallons, and this would cost him 4 * 6.25 = 25 dollars. Thus, the cost efficiency of premium gasoline is 100/25 = 4 miles/dollar.

We see that regular gasoline is (5 - 4)/4 x 100 = 25% more cost efficient than premium gasoline.

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Re: When Mark fills his car with regular gasoline, he gets 20 miles/gallon  [#permalink]

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24 Nov 2019, 21:08
for 20miles/gallon cost 4,
25 miles/gallon costs 6.25.
suppose 100 liters of each is bought
20 m/g 400-----2000 miles ....eqn 1
25 m/g 625-----2500 miles.....eqn2
from eqn 1
100----500
125----500
25 per 100 hence 25 percent....hence option D
Re: When Mark fills his car with regular gasoline, he gets 20 miles/gallon   [#permalink] 24 Nov 2019, 21:08
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