FAA Aviation Mechanic General (AMG)Physics, Math and Fluid LinesHard
A technician must mix oil and fuel in a 20:1 ratio for a two-stroke ground support engine. If the fuel tank holds 1 gallon (128 fluid ounces) of fuel, how many ounces of oil should be added?
- A6.4 ounces
- B20 ounces
- C2.5 ounces
- D12.8 ounces
Show answer & explanationAnswer & explanation
Correct answer: A. 6.4 ounces
A 20:1 ratio means 20 parts fuel to 1 part oil. Dividing total fuel by the ratio: 128 oz ÷ 20 = 6.4 ounces of oil needed.
Why the other options are wrong
- B. Confuses the ratio number with the ounce quantity.
- C. Results from an unrelated calculation error.
- D. Results from dividing by 10 instead of 20.
Ratio Mixing Math
Mixture ratios such as 20:1 indicate parts of one substance per one part of another; dividing the total volume by the ratio number gives the smaller component's amount.
- Ratio X:1 means X parts of first substance per 1 part second
- Divide total volume of the larger part by the ratio number
- Common in two-stroke oil/fuel mixing and cleaning solutions
- Always confirm units match before dividing
Memory trick: Divide the big number by the ratio to find the little ingredient.