Ratios & Proportional Relationships · Grade 7 · 7.RP.A.2.b
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Finding the Constant of Proportionality
Name
Date
Correct / 9
1
Read k Out
- k is the amount for exactly one x. No table below shows x = 1: divide to find k.
1. From the table:
| x | 4 | 6 | 10 |
| y | 10 | 15 | 25 |
k =
2. From the graph:
k =
3. From the equation:
y = 0.35x
k =
4. From words: a printer prints 90 pages every 2 minutes.
k = pages per minute
Ratios & Proportional Relationships · Grade 7 · 7.RP.A.2.b
Roots of Reason
rootsofreason.org
2
Write k In
- now k is given. Build the representation around it.
5. k = 4. Complete the table.
| x | 3 | 5 | 9 |
| y |
6. k = 2/3. Write the equation.
y =
7. k = 1.5. Draw the line, then mark the point for x = 2.
3
Say What k Means
- write what k means with its units, like $2.50 per pound.
8. Three equal bags weigh 12 kg in all.
?
?
?
= 12 kg
k = kg per bag, so y =
9. y = 0.35x gives the cost y, in dollars, of x ounces of candy. Finish the sentence.
One ounce costs
Ratios & Proportional Relationships · Grade 7 · 7.RP.A.2.b
Roots of Reason
rootsofreason.org
Finding the Constant of Proportionality
1Read k Out
1. From the table:
10 ÷ 4 = 15 ÷ 6 = 25 ÷ 10 = 2.5
k = 2.5
2. From the graph:
3 up for every 4 across. Less than 1 is fine
k = 3/4
3. From the equation:
k is the number multiplying x
k = 0.35
4. From words: a printer prints 90 pages every 2 minutes.
90 ÷ 2 = 45, for exactly ONE minute
k = 45 pages per minute
Ratios & Proportional Relationships · Grade 7 · 7.RP.A.2.b
Roots of Reason
rootsofreason.org
2Write k In
5. k = 4. Complete the table.
| x | 3 | 5 | 9 |
| y | 12 | 20 | 36 |
6. k = 2/3. Write the equation.
y = (2/3) x
7. k = 1.5. Draw the line, then mark x = 2.
3Say What k Means
8. Three equal bags weigh 12 kg in all.
4
4
4
= 12 kg
12 ÷ 3 = 4 for one bag
k = 4 kg per bag, so y = 4x
9. y = 0.35x gives the cost y, in dollars, of x ounces of candy. Finish the sentence.
k = 0.35 dollars per one ounce
One ounce costs $0.35 (35 cents)