It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

A word I know has six letters it contains, remove one letter and 12 remain. What is it?

When it's bad luck to meet a black cat?

A swan sits at the center of a perfectly circular lake. At an edge of the lake stands a ravenous monster waiting to devour the swan. The monster can not enter the water, but it will run around the circumference of the lake to try to catch the swan as soon as it reaches the shore. The monster moves at 4 times the speed of the swan, and it will always move in the direction along the shore that brings it closer to the swan the quickest. Both the swan and the the monster can change directions in an instant.
The swan knows that if it can reach the lake's shore without the monster right on top of it, it can instantly escape into the surrounding forest.

How can the swan successfully escape?

ENEMY = 2 * LINK
LINK + 2 = HELL

Then what will be TAXI + HELL? Select from the options below:
a) ROTTEN
b) DANGER
c) HEAVEN
4) MORTAL

How do you go from 98 to 720 using just one letter?

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

Can you find out the remainder when 3^300 is divided by 5?

How can a man go eight days without sleep?