To determine how many gallons of perfume will be in each container, we need to divide the total amount of perfume (10.5 gallons) by the number of containers (3.5 * 10²).
First, we calculate the number of containers: \[ 3.5 \times 10^2 = 3.5 \times 100 = 350 \text{ containers} \]
Next, we divide the total amount of perfume by the number of containers: \[ \frac{10.5 \text{ gallons}}{350 \text{ containers}} = 0.03 \text{ gallons per container} \]
Finally, we express 0.03 in scientific notation: \[ 0.03 = 3.0 \times 10^{-2} \]
Thus, each container will have \( \boxed{3.0 \times 10^{-2}} \) gallons of perfume.