Final answer:
The correct system of equations to model Ellie's situation is 0.5c = 4.5f and 0.5c + 2.25f = 10. This system reflects the requirement of using twice as much sugar for cookies as for fudge, and the total sugar used not exceeding the 10-pound bag she has.
Step-by-step explanation:
Ellie has a 10-pound bag of sugar and wants to use twice as much sugar for cookies as for fudge. If c represents the number of batches of cookies and f represents the number of batches of fudge, we can establish the following relationships:
- Each batch of cookies requires 0.5 pounds of sugar, so the total sugar for cookies is 0.5c.
- Each batch of fudge requires 2.25 pounds of sugar, so the total sugar for fudge is 2.25f.
- Ellie wants to use twice as much sugar for cookies as for fudge, which gives us the equation 2(2.25f) = 0.5c or 4.5f = 0.5c.
- All the sugar used must add up to 10 pounds, which gives us the second equation 0.5c + 2.25f = 10.
Combining the two equations, we can form a system of equations that models the situation:
- 0.5c = 4.5f
- 0.5c + 2.25f = 10