# Math Help - geometry

1. ## geometry

Since I got such a fast reply to my last post I figured I'd go ahead and post for help on this one. I am stuck this time because I don't understand the depth when V=L (660) x W (660) x D (?)?

---a) If 18 inches of water are evaporated from an artificial lake that is 660 feet long and 660 feet wide, what is the volume of water that evaporated in gallons? b) If annual precipitation adds 9 inches to the lake and annual discharge adds 108, 900 ft2, what would be the net loss of water from the lake in ft3?---

2. Consider only the evaporated water volume. It is a prism, having volume
$V = \underbrace{660ft}_{length} \times \underbrace{660ft}_{wideness} \times \underbrace{(18in = 1.5ft)}_{depth} = 653 400 ft^3$
Now just convert it into gallons:
$V = 653 400 ft^3 \simeq 4 887 771 gal$
The approach for letter (B) is very similar to this, so I leave it to you as an exercise.

TIP: describe the subject of your doubt in the topic title, as it tends to give you even faster answers.

3. i assume part b) is a continuation of a), so don't I just add 9 inches (make it 0.75 feet) and 108, 900 ft2 to the 653,400 ft3 found in the first part of the question? 108900.75 + 653400=762300 ft3