SOLUTION: Bob drove 408 miles using 15 gallons of gas. At this rate, how many gallons of gas would he need to drive 340 miles?

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Question 465792: Bob drove 408 miles using 15 gallons of gas. At this rate, how many gallons of gas would he need to drive 340 miles?
Found 2 solutions by solver91311, kingme18:
Answer by solver91311(16897) About Me  (Show Source):
You can put this solution on YOUR website!




Cross multiply and solve the resulting single variable linear equation for

John

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Answer by kingme18(98) About Me  (Show Source):
You can put this solution on YOUR website!
You can solve this using a proportion, which basically means a fraction = a fraction. For both, I'm going to put the number of miles over the number of gallons; if you want, you can put gallons over miles as long as you do it both times. 408%2F15=340%2Fx. My favorite way to solve this is to do cross multiplication: multiply the top left with the bottom right, and multiply the bottom left with the top right. 408%2Ax=15%2A340. Simplify: 408x=5100. Divide by 408 on both sides to get x by itself, and your final answer is x=12.5.

I like to go back and check by doing the division on both sides and making sure I get the same thing for both: 408%2F15=27.2 and 340%2F12.5=27.2. Both fractions equal 27.2, so we're definitely right!