Question

A caterer needs to buy 21 pounds of pasta to cater a wedding. At a local store, 8 pounds of pasta cost $12. How much will the caterer pay for the pasta there?

1. Write a ratio for the given information about the cost of pasta



2. Would it be more helpful to write an equivalent ratio with 1 pound of pasta as one of the numbers, or with $1 as one of the numbers? Explain your reasoning, then write that equivalent ratio.




3. Find the answer and explain or show your reasoning.

Answer 1

1. 8/$12=21/$x then cross multiply.

2. 1/$1.5, we're looking for cost so $1 is more reasonable

3. $31.5

Explanation:

12x 21/ 8 = 31.5

Answer 2

$31.50

Explanation:

To solve this problem, we need to use the rule of three, which is based on ratios and proportional relationships.

The ratio that shows the cost of pasta is:

`(\$12)/(8 lb)`

Which means that they charge $12 per 8 pounds of pasta.

Now, it would be help if we use the given ratio to apply the rule of three. Looking for a ratio per pound of pasta would be waste of time, and could confuse a lot. So, we just use the given ratio.

If 8 pounds of pasta costs $12, how much would be 21 pounds of pasta?

`x=21 \ lb(\$12)/(8 \ lb)=\$ 31.50`

Therefore, according to the given ration, it would cost $31.50 to get 21 pounds of pasta.