Car A gets 25% more miles per gallon of gasoline than car b does. However, car A requires special gas that is costs 10% more than the gas for car b uses. If the two cars are driven equal distances, what percent less than the money spent on gasoline for car b is the money spen on gas for car a.
a.22.5 %
b.17.5%
c.15%
d.12%
e.10%
qa is D, I am having some good troubles with tranlsating the equations out of here. How can I get better at this? THis shouldnt be this difficult!
kaplan word problem
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Setup Grid
Assume B does 100 miles/gallon and cost of fuel for B is 100$/gallon
Car || Miles/Gallon || Cost/Gallon || Cost/Mile
B || 100 || 100 || 1
A || 125 || 110 || 110/125
Percentage difference in costs is (B-A)/B * 100
solve and get 12.
Excuse the 'grid' it doesnt really display nice here. But hopefully you get the idea.
Assume B does 100 miles/gallon and cost of fuel for B is 100$/gallon
Car || Miles/Gallon || Cost/Gallon || Cost/Mile
B || 100 || 100 || 1
A || 125 || 110 || 110/125
Percentage difference in costs is (B-A)/B * 100
solve and get 12.
Excuse the 'grid' it doesnt really display nice here. But hopefully you get the idea.
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Percent question with unspecified values - perfect for picking numbers.Enginpasa1 wrote:Car A gets 25% more miles per gallon of gasoline than car b does. However, car A requires special gas that is costs 10% more than the gas for car b uses. If the two cars are driven equal distances, what percent less than the money spent on gasoline for car b is the money spen on gas for car a.
a.22.5 %
b.17.5%
c.15%
d.12%
e.10%
On most % questions, we want to pick 100. To keep things as simple as possible, let's let 100 be the unmodified quantities.
So:
b gets 100 mpg
a gets 125 mpg (25% more than b)
1 gallon of b gas costs $100
1 gallon of a gas costs $110 (10% more than b)
Let's pick a number of miles that works easily with both a and b: the LCM of 100 and 125 is 500, so that's a great choice.
Let d = 500
at 100mpg, it takes car b 5 gallons of gas and it takes car a 4 gallons of gas.
b pays $100 per gallon, so b pays $500
a pays $110 per gallon, so a pays $440
The question is what % less does a pay than b, so we want:
(amt b - amt a)/(amt b) = 60/500 = 12/100 = 12%: choose (d).
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I saw where I went wrong. I made things way more complicated than they needed to be. With your advice here is a way that I would approach it next time. I do best when I simply logically answer the question. It is much easier, faster and accurate than setting up lengthy complicated compuations. I am just sticking to the golden simple rule taught me by kaplan and manhattan gmat.
heres the new approach:
Pick number:
A=125 mpg B=100 mpg A gas= $11 and B gas = $10
Distance is set to 500 miles
So, gallons of gas needed for A= 500/125= 4
gallons of gas needed B= 500/100=5
Cost of trip: A:4 X $11= 44 and cost of trip B: 5x10=$50
now simply stick into percent change formula
(50-44)/50= .12 qa is d
heres the new approach:
Pick number:
A=125 mpg B=100 mpg A gas= $11 and B gas = $10
Distance is set to 500 miles
So, gallons of gas needed for A= 500/125= 4
gallons of gas needed B= 500/100=5
Cost of trip: A:4 X $11= 44 and cost of trip B: 5x10=$50
now simply stick into percent change formula
(50-44)/50= .12 qa is d
Appetite for 700 and I scraped my plate!
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