Question

Your car uses gasoline at the rate of 21 miles per gallon. If gasoline costs $2.82 per gallon, and you drive for 7 hours at a speed of 48 miles per hour, how much will you pay for gasoline for the trip?

A. $38.18
B. $45.12
C. $47.73
D. $59.27

so 21 miles = 1 gallon
7 hours (48 miles/hour)= 336 miles?
after that im lost.. X< someone please help :D im confused thanks !

Answer 1

Make an "identity" out of "21 miles = 1 gallon" by creating a fraction of "1 gallon" in the numerator and "21 miles" in the denominator. Multiply that by what you (correctly) determined was the total mileage.

Answer 2

Then multiply the answer from my first post by another identity:

$ 2.82 in the numerator and "1 gallon" in the denominator.

Answer 3

im still lost @tcarroll010

Answer 4

I'm not sure why you're lost. I can't say it any plainer or simpler. Plus, all I'm doing is expanding on the method you are already using.

Answer 5

d?

Answer 6

You already created an identity or fraction out of miles per hour when you determined the mileage. It's just doing the same thing with the other variables.

Answer 7

So, if you show your work, and that means all of it, every step, I can see if you are doing anything wrong. You just might end up doing everything right.

Answer 8

21 miles/ gallon
costs $2.82/gallon
so, 21(2.82)=59.22(7hours) 48 miles/hour
=48(7)=336 after that i dont know what to do

Answer 9

(7 hrs) x [(48 miles)/hr] x [(1 gal)/(21 miles)] x [($2.82)/gal]

All your units will cancel except dollars. Eventually, you will not need to put the units in the calculation, but in the beginning it helps.

Answer 10

What might be confusing you in your way of trying to do the problem, is that you are trying to set up an equation. This instead is merely an expression (no "equals" sign). Mathematically, you are just restating what "7 hours" is. You have 4 factors. The result of the first 2 factors is in miles. The result of that (the first 2 factors) and the third factor is in gallons. The result of that (the first three factors) and the fourth factor is in dollars.

Answer 11

All good now, @panda03 ?

Answer 12

yeeeeeeeeeeeeeees thank you.. im thinking to hard thats all.. too much interruptions and ive been solving problems :( thank you for making me understand tho @tcarroll010

Answer 13

haha done @tcarroll010 ur welcome

Answer 14

uw! Good luck to you in all of your studies and thx for the recognition! @panda03