I am having trouble with solving measurment word problems

Question

The problem goes as follows

A swimming pool is 15 by 30 ft and a consistent 5 ft deep. You are painting he walls and floor of the pool. If a gallon can of paint covers 250 square feet how many gallons of cans would you need to buy?

How to solve this

Answer 1

You need to compute the total area of the five sides of the pool that you will paint, then divide by the area covered by one gallon to get the number of gallons used. Then round up if necessary because you can only buy full cans.

Answer 2

The total area of the swimming pool is the sum of 5 areas:

• Two times a wall with width of $15$ ft and depth of $5$ ft.

The area of one wall is $15 \text{ft} \cdot 5\text{ft}=75 \ \text{ft}^2$

Therefore both walls have an area of $2\cdot 75 \ \text{ft}^2=150 \ \text{ft}^2$

• Two times a wall with length of $30$ ft and depth of $5$ ft.

Similar calculation like above.

• One times a wall with length of $30$ ft and width of $15$ ft.

The area of this wall is $30 \ \text{ft} \cdot 15\text{ft}=450 \ \text{ft}^2$

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Sum up the all 5 areas. And finally divide this sum by $250 \ \text{ft}^2$.