Solve estimation and probability brainteasers

Answer the following independent brainteaser questions. State any assumptions you need.

1. Tile a floor : A floor is 15 ft × 20 ft . You will cover it with square tiles of area 1 square yard each. Approximately how many tiles are needed?
2. Doubling account : An account starts with $1000 and doubles every year . How much is in the account after 20 years ?
3. Estimate Earth–Moon distance : Sitting by a window and looking at the Moon, estimate the distance from you to the Moon using reasonable “back-of-the-envelope” reasoning.
4. Stones in a boat : A boat is floating in a lake with some stones in it. You throw the stones into the lake. Does the lake’s water level rise, fall, or stay the same?
5. Probability of even product : There are two boxes . Each box contains three cards labeled 1, 2, 3 (one of each). You draw one card from each box (uniformly at random). What is the probability that the product of the two numbers is even ?
6. Uncompressed 1080p movies on a 2 TB drive : Approximately how many uncompressed 1080p movies can fit on a 2 TB hard drive? Clearly state assumptions (frame rate, color depth/bytes per pixel, movie length, TB definition).
7. Nested squares area : Three squares are “nested” one inside another (concentric), with each inner square formed by connecting the midpoints of the sides of the previous square. If the innermost square has area $A$ , what is the area of the outermost square?