Question

You drive 75 miles and use 3 gallons of gas, at the same ratio, how may miles can you drive with 12 gallons of gas?

Answer 1

When you say "at the same ratio", you mean that you consume the same amount of gas for the same amount of miles.

We know that everytime you drive 75 miles, you use 3 gallons of gas.

Since 12 gallons of gas is four times 3 gallons of gas, if the ratio remains the same, you can drive four times the distance:

You drive 75 miles, and use 3 gallons.

You drive 75 more miles (so you are at $75+75 = 150$ miles) and use 3 more gallons, so you use $3+3 = 6$ gallons.

You drive 75 more miles (so you are at $150+75 = 225$ miles) and use 3 more gallons, so you use $6+3 = 9$ gallons.

You drive 75 more miles (so you are at $225+75 = 300$ miles) and use 3 more gallons, so you use $9+3 = 12$ gallons, and you're done.