Question

Ritchie wants to paint his bedroom ceiling and four walls. Both the ceiling and walls are 8 by 8 feet. A gallon of paint covers 40 square feet. Which expression can be used to find the number of gallons of paint Ritchie needs to buy?

Answer 1

Answer:

Option C is correct.

Number of gallons of paint Ritchie needs to buy;  $8^2(4+1) \div 40$

Step-by-step explanation:

Unit rate defined as the rates are expressed as a quantity as 1 such as 8 miles per hour or 5 meter per second.

As per the statement: Ritchie wants to paint his bedroom ceiling and four walls. Both the ceiling and walls are 8 by 8 feet.  

Area of four wall = $4 \cdot \text{Area of each wall} = 4 \cdot (8 \times 8) = 4 \cdot (8^2)$ square feet

also;

Area of ceiling = $8 \times 8 = 8^2$ square feet

Total area of ceiling and four walls = $4 \cdot 8^2 + 8^2 = 8^2(4+1)$ square feet.  {Using distributive property $a \cdot (b+c) = a\cdot b+ a\cdot c$ }

Also, it is given a gallon of paint cover 40 square feet.

⇒Unit rate per area = $\frac{1}{40}$ gallon of paint

We have to find the number number of gallons of paint.

$\text{Number of gallons of paint} =\text{Unit rate per area} \times \text{Total number of area of both ceiling and four walls}$

Substitute the given values we get;

$\text{Number of gallons of paint}=\frac{1}{40} \times \{8^2 (4+1)\}$

Inverse of Multiplication operation is Division.

Therefore, number of gallons of paint Ritchie need to buy is, $8^2(4+1) \div 40$