ANSWER:
11 gallons
Explanation:
We can calculate the amount of gallons to be able to whistle 7 rooms by means of the following proportion:
![(4.5)/(3)=(x)/(7)](https://img.qammunity.org/2023/formulas/mathematics/college/ofaucqrtj7jnyjiukpmde74ye14g5xd5ha.png)
Let x be the number of gallons needed, we solve for x:
![\begin{gathered} x=(4.5)/(3)\cdot7 \\ \\ x=10.5\approx11\text{ gallons} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/boi0jwrrmk69ueyad9nupfhvcf71hxzvvx.png)
Since they must be whole gallons, it takes 11 gallons to paint 7 rooms.