The SpongeBob Equation

Question

SpongeBob SquarePants is helping Mr. Krabs place an order for the Krusty Krab. SpongeBob has decided to order cod (which is $3 a pound) and salmon (which is $8 a pound). He needs to buy at least 40 pounds of fish, but Mr. Krabs is a cheapskate and has told him he can spend a maximum of $240.

Answer 1

Hello, Charles,

Enter the data into a table (Mine wouldn't fit here).

Let's let C and S stand for lbs of Cod and Salmon. Multiply each by its cost/lb: (3C and 8S). The total weight is 40 lbs, so C+S=40. The total cost is 3C+8S=240.

Rewrite C+S=40 as C=40-S. Then use that value of C in the total cost equation and solve for S. Then subtract that number(24lbs of Salmon) from 40lbs to get 16lbs of Cod. Enter those values in the first table and check to see if 24lbs of Salmon and 16lbs of cod add to 40lbs and cost $240.

I found 16lbs of Cod and 24lbs of Salmon would fit the requirements of 40lbs total weight and $240 total cost.

Bob

Answer 2

3C + 8S = 240

C + S = 40

-3 * Eq2 + eq1:

5S = 120

S = 24

C = 16

check

3(16) + 8(24) = 48 + 192 = 240

16 pounds of Cod

24 pounds of Salmon