1. **State the problem:** Ritchie wants to paint his bedroom ceiling and four walls. Each surface is 8 feet by 8 feet. We need to find an expression for the number of gallons of paint required. 2. **Calculate the total area to be painted:** Each surface area is $8 \times 8 = 64$ square feet. 3. **Count the surfaces:** There is 1 ceiling and 4 walls, so total surfaces = $1 + 4 = 5$. 4. **Total area:** Multiply the area of one surface by the number of surfaces: $$5 \times 64 = 320$$ square feet. 5. **Paint coverage:** One gallon covers 40 square feet. 6. **Expression for gallons needed:** Divide total area by coverage per gallon: $$\frac{320}{40}$$ 7. **Simplify the expression:** $$\frac{\cancel{320}}{\cancel{40}} = 8$$ **Final answer:** Ritchie needs 8 gallons of paint.