My cousin lives in one story house in Antarctica. His house is made the of-of sandstone. what is the color of stairs?

I have two sand hourglasses:
1. A 7 minute one and
2. An 11-minute one.

Using just these 2 sand hourglasses, how can I measure time as 15 minutes?

Can you quickly find which two matchstick figures are identical?

Take one out and scratch my head, I am now black but once was red. What am I?

Can you move 2 matchsticks to form four equal sized squares.

I want to fill my bucket using both cold and hot water.
I have two taps for both cold and hot water. The hot water tap fills the bucket in exact 6 hours and the cold water tap fills the bucket in exact 4 hours.
I turn both of them simultaneously but I forgot to turn off another tap which removes the water out of the bucket. This tap can empty the bucket in 12 hours.

How Long will it take to fill the bucket?

Can you find the thief by just looking at the picture below?

There is a brick of gold and a brick of iron in a boat (both 10-inch blocks), if they are both dropped into the water which will make the water level higher?

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?

A tree doubled in height each year until it reached its maximum height over the course of ten years. How many years did it take for the tree to reach half its maximum height?