This physics problem is really confusing me!?

Question

An average family of four uses roughly 1200 liters (about 300 gallons) of water per day. (one liter = 1000 cm(cubed). How much depth would a lake lose per year if it uniformly covered and area of 50 square kilometers and supplied a local town with a population of 40000 people? Consider only population uses, and neglect evaporation and so on.

Please help!!!

Answer 1

4 meembrs use 12*10^5cmcube/day

40000memebrs use=(12*10^5cmcube*40000)/4=12*10^9cmcub...

in 1 day 12*10^9cmcube is used]

in 365 days=12*10^9cmcube *365=438*10^10

so i 1 day it loses=50*10^10/12*10^9=41.6cm

in 1 yesr=41.6*365=15184cm=0.15km

Answer 2

Im no expert and I think the guy before me might be right but I think its something like this..

population of 40000/ 4 (per family) = 10000 familes

4 people consume 1200 liters => 1200m(cubed)/ day

10000 families consume 12000000 m (cubed / day) = 12000 km (cubed)

Multiply by 365 you get 4380000 km (cubed) year

The lake is 50 km (sqare)

Volume is L x W x H (or depth) and we have the product of L and W

So 4380000 km (cubed) = 50 km (squared)  X (DEPTH)

Depth  = 87,600 Km

Sounds like alot, but it sounds right to me...

Answer 3

1.2e3 L/4 people = 300 L/person

3.0e2 L * 1.0e3 cm³ * 4.0e4  * 3.65e2 = 4.38e12 cm³ /yr

50 km² = 5e11 cm²

4.38e12 cm³ / 5e11 cm² = 8.76 cm

Answer 4

40000people=>10000families=10000*120l=>1...

=4.38e7Fcm^3/year

50,000 * x cm=4,38e7Fcm^3/year

x=876cm.

Answer 5

300L a day is 12000000L for entire population

this is 12000M3 over an area of 50KM2 that is 0.00024M a day times 365days = 0.0876M of 8.76CM