To find the total cost of the apples, you can multiply the weight of the apples by the cost per pound.
Zoe bought 1.5 pounds of apples at $3.50 per pound, so the calculation is:
\[ \text{Total Cost} = \text{Weight} \times \text{Cost per Pound} \] \[ \text{Total Cost} = 1.5 , \text{pounds} \times 3.50 , \text{dollars per pound} \] \[ \text{Total Cost} = 5.25 , \text{dollars} \]
Therefore, the total cost of the apples is $5.25.