Word problem

[datonman]

It's these word problems that I feel are tricky. This one I feel would be solved either using an equation or picking numbers. I'm not sure.

If you hire Mary's Car Service to drive you across town, you will be charged $10 plus an additional $2, for each 1/4 mile. Which of the following represents the total number of dollars that you would be charged if the trip is 'n' miles?

A)2n
B)10+2n
C)10+4n
D)10+8n
E)12n

[DavidG@VeritasPrep]

It's these word problems that I feel are tricky. This one I feel would be solved either using an equation or picking numbers. I'm not sure.

If you hire Mary's Car Service to drive you across town, you will be charged $10 plus an additional $2, for each 1/4 mile. Which of the following represents the total number of dollars that you would be charged if the trip is 'n' miles?

A)2n
B)10+2n
C)10+4n
D)10+8n
E)12n

Algebra: We know there are 4 quarter-miles in each mile. If there are n miles, there are a total of 4n quarter-miles. If the charge is $2/quarter mile, that means 4n*2 = 8n dollars beyond the initial $10 charge. Answer: 10 + 8n, D

[DavidG@VeritasPrep]

Or say n= 1 mile. So you're going 4 quarter-miles. And you're paying $2/quarter mile, so that's $8. Add that to the initial 10, and your cost is $18. Substitute n=1 into the answers and D will give you 18.

[GMATGuruNY]

It's these word problems that I feel are tricky. This one I feel would be solved either using an equation or picking numbers. I'm not sure.

If you hire Mary's Car Service to drive you across town, you will be charged $10 plus an additional $2, for each 1/4 mile. Which of the following represents the total number of dollars that you would be charged if the trip is 'n' miles?

A)2n
B)10+2n
C)10+4n
D)10+8n
E)12n

A $2 surcharge per 1/4 mile implies an $8 surcharge per mile.
Let n = 1 mile.
Cost for a 1-mile trip = ($10 base fee) + ($8 surcharge per mile) = 10+8 = 18. This is our target.
Now plug n=1 into the answers to see which yields our target of 18.
Only D works:
10 + 8n = 10 + 8*1 = 18.

The correct answer is D.

[MartyMurray]

Myself, in this case I would just convert $2 per quarter mile to $8 per mile, and add $10 to get 10 + 8n and be done with it.

For a more complex one it might make sense to plug in numbers if you are not sure how to make the math work otherwise, but getting to the answer to this one is pretty straightforward.