This is non related but an example(I think):
Have some popcorn. How much? Well, not a gallon in one sitting. Figure it out: if there are eight ounces in a cup, and 16 cups in a gallon, how many ounces of popcorn would make one gallon? ( 8 x 16 = ) Whoa! That's too much to eat in one day. But you could probably eat a whole gallon of air-popped, butter-free popcorn in one week, and feel great!
Supplies:
Scratch paper and pencil
Do you know how to figure out how many miles per gallon of gas a car gets? You look in the owner's manual to see how many gallons of gas the car's tank holds. Then you fill it up with gas, and write down the mileage from the odometer.
Next time you fill 'er up with gas, you write down how many gallons the tank took. With that information, you can compute how many miles you drove, and how much gas you used.
      All you do is subtract the old mileage from the new mileage, and divided that by the number of gallons you just put in your car.
      Let's say the last time you got gas, you had 20,175 miles on the odometer. You put in 10 gallons of gas 'til your tank was full. This time, you had 20,325 miles on the odometer, and you filled it up again.
                                 20,325
                                - 20,175
                                   150
(So: miles driven on 10 gallons of gas = 150 ÷ 10 = 15 miles per gallon of gas)
      You could put a small notebook in your car's glove box, and every time your family gets gas, the total gallons and price should be recorded. Also write down whether you were mostly driving around doing errands on the city, or count up your highway miles; cars are generally more gas-efficient when they're driven steadily at a pretty fast speed without a lot of starting and stopping.
Then once a month or so, you can look at the numbers with a grownup, and figure out what your gas mileage is.
Another example:
Let's say your vehicle's tank holds 20 gallons and the odometer shows 10,000 miles. Next time you get gas, your vehicle takes in six new gallons to get to "F" for full. Your odometer shows 10,120 miles. Subtract the 10,000 miles you started with from the 10,120 miles it shows now. That means you went 120 miles on six gallons of gas. Divide the 120 by 6, and you'll come up with 20. That means you got 20 miles per gallon. Not great. But not bad!
      The miles per gallon will differ significantly with the type of vehicle that's being used, how fast it goes, how much it weighs, and what type of movement it's making. For example, a Formula 1 racing car gets just over 3 miles per gallon - significantly less than your family car, no doubt:
