Can you make four (4) nines (9) equal 100?

I am a type of food that is often found in the fridge and can be white in colour. What I am?
Hint 1: I am a dairy product.
Hint 2: You can spread me on the bread.

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

Analyze and find the missing item in the sequence:
16, 06, 68, 88, __, 98

Can you calculate the probability of getting a sum of six when a dice is thrown twice?

A beggar on the street can make one cigarette out of every 6 cigarette butts he finds. After one whole day of searching and checking public ashtrays the beggar finds a total of 72 cigarette butts. How many cigarettes can he make and smoke from the butts he found?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

A mother is 21 years older than her child. In exactly 6 years from now, the mother will be exactly 5 times as old as the child.
Where's the father?

A man started to town with a fox, a goose, and a sack of corn. He came to a stream which he had to cross in a tiny boat. He could only take one across at a time. He could not leave the fox alone with the goose or the goose alone with the corn. How did he get them all safely over the stream?

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?