A ratio is a comparison between two numbers. They can be expressed as either fractions or two numbers separated by a colon. Ratio best practice – it is much easier to solve problems if you always organize your information in fraction format. Label the information to keep track of vital facts and to avoid careless errors. Remember to use the standard word problem approach when you encounter a word problem that involves ratios.
Example
Color X ink is created by blending red, blue, green, and yellow inks in the ratio 6:5:2:2. If the batch contained 30 liters of color X ink, what is the number of liters of green ink that was used to create the batch of color X ink?
- 3
- 4
- 5
- 6
- 15
The Solution
- The question is asking many liters of green ink were used to create a certain batch of color X ink
- Assign variables. Since all we are solving for is the number of liters of green ink, let x = # liters green ink
- When you see a ratio problem, immediately organize the information provided in fraction form and label accordingly.
- Solve
r = 6
b = 5
g = 2
y = 2
Define a mathematical relationship. Since are trying to solve for the total number of green ink, we can setup a proportion. The number of green ink to the total ink mixture is 2:15 (sum red, blue, green, and yellow = 15). If the final volume is 30, x will give us the total amount of green in the batch.
x is equal to 4, there are 4 liters of green in the batch. The answer is B.
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