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

John is pretty weird. He likes toffees but hates chocolates. He loves books but never reads. He likes to build his troops in an online game but does not proceed with the war. He likes to go swimming but is afraid of water.

Seeking this behaviour, can you tell whether he likes balloons and parties?

What is the centre of gravity?

Count the number of triangles in the given picture.

The person who makes it has no need for it; the person who buys it has no use for it. The person who uses it can neither see nor feel it. What is it?

No matter how little or how much you use me, you change me every month. What am I?

Why do people go to bed?

John and Jenni are a married couple. They have two kids, one of them is a girl. Assume safely that the probability of each gender is 1/2.
What is the probability that the other kid is also a girl?

Hint: It is not 1/2 as you would first think.

What kind of tree can you carry in your hand?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?