Solution:

15/4 hours

Explanation:
Let us say they drive for "t" hours and initial fuel is "f"
Amount of fuel consumed by Fernando car is ft/4
Amount of fuel consumed by Sebastian car is ft/5

As per given condition,
f - ft/5 = 4(f-ft/4)
t = 15/4 hours

Solution:

The two numbers are 4 and 13 whose product is 52 and sum is 17.

Solution:

13 x 3 + 1 = 40

The number of decks is absolutely not relevant here which means whether we mix 5 or 500 cards still results would be same.
Any card drawn will be a Ace,2,3,4,5,6,7,8,9,10,Jack,Queen or King, so there are 13 possibilities each time a card is drawn.
If you are lucky just 5 cards of the same kind can be obtained in 4 steps

The unluckiest(worst) way is our solution as we need to guarantee a four of a kind.
Draw 3 of each kind =>now we have 39 cards. Next card will guarantee 4 of a kind.

Solution:

Here is a way to do it. We dont know if it can be done using some other arrangement or not. If you know, do send us.

4 | 3 | 8
9 | 5 | 1
2 | 7 | 6

Solution:

The clerk said that every day the password is CHANGED. Changed is the password.

Solution:

1. Fill 5 liters jar ( 5l-jar:5, 3l-jar:0)
2. Transfer to 3 liters pail (5l-jar:2, 3l-jar:3)
3. Empty 3 liters jar ( 5l-jar:2, 3l-jar:0)
4. Transfer 2q from 5 pail to 3 pail (5l-jar:0, 3l-jar:2)
5. Fill 5 liters pail(5l-jar:5, 3l-jar:2)
6. Transfer 1q from 5 pail to 3 pail(5l-jar:4, 3l-jar:3)

Solution:

On the back, since bullet train is accelerating, therefore,the person at the back will spend less time than one in front.

Solution:

He askes the god to beat him half to death.

Solution:

I + IX = X

The equation read from the other side becomes X = XI + I which is false.

Solution:

The Password.

Explanation:
Clues 2 and 5 are correct and rest are lies.

Solution:

I am Spice

Explanation:
Spice is hot if you remove first two alphabets then it will become "ice", which is really cold.