Lisa's pet shop has 2 fish tanks. Tank A contains smaller fish who are fed 1 gram of food each per day. Tank B contains larger fish who are fed 2 grams of food each per day. If Tank B contains 2/3 the number of fish that Tank A contains, will Lisa ever feed both tanks the same amount of food? How many of each type of fish of fish would she need to have?
Answer:
in tank A, we need 1 gram of food per fish.
In tank B, we need 2 gramms of food per fish.
If Na is the number of fish in tank A and Nb is the number of fish in tank B.
Then, the amount of food that the tank A needs is:
Na1g of food
The tank B needs:
Nb2g of food
And we know that Nb = 2/3Na
we can replace it and get:
2/3Na2g
Then if both tanks need the same amount of food, we should have that both of these equations are equal:
food of tank A = food of tank B
Na1g = (2/3)Na2g
we solve this for Na
Na = (2/3)Na2g/1g = (2/3)Na2 = (4/3)Na
Na = (4/3)Na
This equation has no solution, and from here we can conclude that if Nb = 2/3Na, she will never give the same amount of food to both tanks.
b) knowing that the amount of food neded in tank A is half the amount for tank B, then we need the doulbe of fish in the tank A than in the tank B
Na = 2Nb