FlashKeepers

Math · K-12

Ratios and Proportions Facts

Setting up and solving ratio and proportion problems, including unit rates and scale factors, for middle school math.

34 cards · basic cards · AI-written, checked twice. Edit anything.

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What is a ratio?
A comparison of two quantities using division.
Write three ways to express the ratio of 3 to 5.
3:5, 3/5, or 'three to five'.
What are equivalent ratios?
Ratios that represent the same comparison, like 2:3 and 4:6.
To simplify a ratio, what do you do?
Divide both numbers by their greatest common factor (GCF).
Simplify the ratio 8:12.
2:3 (divide both by 4, the GCF).
What is a unit rate?
A ratio that compares a quantity to one unit of another quantity.
If 5 apples cost 10 dollars, what is the unit rate?
2 dollars per apple (divide 10 by 5).
If you travel 150 miles in 3 hours, what is your unit rate?
50 miles per hour.
What is a proportion?
An equation that states two ratios are equal.
What is cross multiplication?
A method for solving proportions: multiply the numerator of each fraction by the denominator of the other.
Solve: 3/5 = x/10. Find x.
x = 6 (cross multiply: 3 times 10 = 5 times x, so 30 = 5x).
Solve: 2/3 = 8/x. Find x.
x = 12 (cross multiply: 2 times x = 3 times 8, so 2x = 24).
What is a scale factor?
A multiplier that describes how much a figure is enlarged or reduced.
If a scale factor is 3, how does the figure change?
The figure is enlarged; all dimensions are multiplied by 3.
If a scale factor is 1/2, how does the figure change?
The figure is reduced; all dimensions are multiplied by 1/2.

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