PROPORTIONAL
RELATIONSHIPS
What is a ratio?
◦ A comparison
between two numbers
What is a proportion?
◦ A proportion is an equation showing that two ratios are equal
Why do we use ratios?
◦ Ratios can help us find rates, convert recipes or compare
objects.
◦ A car travels 75 km in 5 hours. (rate)
◦ We want to make 2 cakes. One recipe calls for 3 cups of flour.
◦ There are 5 apples purchased at the grocery store for every 3 oranges.
A car travels 75 km in 5 hours.
◦ How many km have they travelled after 1 hours?
◦ How many km have they travelled after 2 hours?
◦ How many km have they travelled after 10 hours?
Hours
Km
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A car travels 75 km in 5 hours.
Hours
km
1
15
2
30
5
75
10
150
Direct Variation
A car travels 75 km in 5 hours.
Hours
km
1
15
2
30
5
75
10
150
How do we find our constant of
variation? (constant of proportionality)
◦ If 𝑦 = 𝑘𝑥 then 𝑘 =
Hours
km
1
15
2
30
5
75
10
150
𝑦
𝑥
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