Hello, please help me solve this question

Question

A car uses 3 gallons of gas to go 48 miles. How many gallons will it use on a 320 mile trip?

Answer 1

Hi Iris;

A car uses 3 gallons of gas to go 48 miles. How many gallons will it use on a 320 mile trip?

(3 gallons)/(48 miles)=(x)/(320 miles)

The units of miles is in the denominators of both equations.  It cancels...

(3 gallons)/(48 miles)=(x)/(320 miles)

(3 gallons)/(48)=(x)/(320)

The only unit remaining is gallons.  This is what we want.

Let's simplify...

(1 gallon)/(16)=(x)/(320)

Cross-multiply...

320 gallons=16x

Divide both sides by 16...

(320 gallons)/(16)=(16x)/(16)

20 gallons=x

 

 

Answer 2

Let's simplify the first part by taking the miles and dividing it by the number of gallons

 

3 gallons for 48 miles = 1 gallon for 16 miles

 

Now we take the 320 miles and divide it by the 16 miles in order to get the gallons

 

320/16 = 20 gallons

 

Then you can double check your answer: 20 gallons, at 16 miles to the gallon, will be spent on a 320 mile trip

20*16 = 320