Question

A swimming pool is 15 ft wide, 25 feet long and 6 feet deep. how much paint is needed to cover the interior of the pool

Answer 1

Given: d=6, l=25, w=15

need to find areas of all surfaces but the top because its a pool and the top is exposed:

2ld + 2dw + lw
2(25)(6) + 2(6)(15) + (25)(15) = 
300        + 180        + 375        = 855 ft²

you need to paint 855ft² of interior surface of the pool. the question asked how much paint is needed though, so there is not enough info provided to answer that. once you know how much paint covers 1ft² then you can multiply by 855.  

Answer 2

2 wide walls (15x6)x2=180 square feet
2 long walls (25x6)x2=300 square feet
ground 25x15=375 square feet

sum them all up and you get
375+300+180=855

you need paint for 855 square feet