how do I know how to find the constant of the proportianlity

Question

Lance is knitting a blanket and needs to buy some more yarn. At his local craft store, 2 balls of yarn cost $5 and 8 balls of yarn cost $20. What is the constant of proportionality in this direct variation situation?

A.
B.
C.
D.
Reset

Answer 1

To find the constant of proportionality in this direct variation situation, we need to set up a proportion using the given values.

Let's let x represent the number of balls of yarn and y represent the cost in dollars.

From the information given, we can set up the following proportion:

2/5 = 8/20

Now, we can cross-multiply to solve for x:

20 * 2 = 5 * 8

40 = 40

Therefore, the constant of proportionality is 2.

So, the correct answer is A.