Solution:

They used the planks in the manner that is shown in the figure.

Solution:

If you build a house on the South Pole, all of its walls will face towards North.

Solution:

3 3/4 hours

Explanation:
Suppose that the amount of petrol in each of the cars in the beginning was M.
Now, suppose that they drove for X hours.

In that case, the amount of petrol used by one car in X hours will be = M*X /4
The amount of petrol used by the other car will be = M*X/5

Therefore, the petrol left in one car = M - M*X / 4
Petrol left in the other car = M - M*X / 5

Now, according to the question,
M - M*X / 5 = 4 (M - M*X / 4)
=> X = 15 / 4 = 3 3/4 hours.

Therefore Murphy and Cooper drove for 3 3/4 hours.

Solution:

doughnut

Solution:

18

Explanation:
More minutes implies more tea.
More women implies more tea.

The time become twice (3 minutes / 1.5 minutes).
women become six times (9 / 1.5).

Number of tea = 2 * 6 * Original(1.5)
= 18

Solution:

The password is U472BMT.

Read aloud the line and you will sound something like "U Four Seven 2 B M T".

Solution:

4 6 5 3 (from magician perspective)
3 5 6 4 (viewer perspective)

Detail:

From user perspective:
3 5 6 4 => 5 6 4 3 => 6 5 4 3

For magician perspective
3 4 5 6 (ascending order as)

Solution:

30 squares.

Explanation:
Assuming smallest square side is 1 meters, then

Total number of squares with side 1 meters are 16
Total number of squares with side 2 meters are 9
Total number of squares with side 3 meters are 4
Total number of squares with side 4 meters is 1

summing 16+9+4+1 = 30

Solution:

Q>P

Explanation:
P = 60 * 60 * 24 seconds = 86, 400 seconds.
Q = (8 * 365 *24) + (2 * 366 *24) hours = 87, 648 hours

Therefore, Q is greater than P. If the leap years were not counted, results would have been different.

Solution:

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