The cost of two walnuts varies proportionality with weight
a two pound bag costs $5
a five pound bag costs $12.50
write an equation that describes the relationship between w, the weight in pounds of the walnuts and c, cost in dollars

ANSWER:  

The cost of two walnuts varies proportionality with weight.The equation is c = 2.5w

SOLUTION:

Given, the cost of two walnuts varies proportionality with weight a two pound bag costs $5, a five pound bag costs $12.50.

Let the proportionality constant be x.

According to the given information,

c = xw --- (1)

Where, c is cost in dollars.

x is proportionality constant

w weight of walnuts in pounds

Given that, a two pound bag costs $5  

Here, c = 5 and w = 2

So, substitute above values in (1)

5 = x(2)

x =

x = 2.5

We have another case also, so let us check it also.

A five pound bag costs $12.50

Here, c = 12.50 and w = 5

So, substitute above values in (1)

12.5 = x(5)

x = = 2.5

So the value of proportionality constant is 2.5

Hence, the equation is c = 2.5w