Why Aeroplane windows are round?

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

You need to pick one entry from pot A and one from pot B to have a perfect match. Can you do it?

You are presented with three boxes. One of them has a red ball inside and the other two have a black ball inside each of them. You are asked to pick up the one with red ball and you pick one. Now, one of the other boxes is opened and it is found to have a black ball.

You are presented with a chance to change your box with the one that is left closed. Will you change your box? Why or why not?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

What number do you get when you multiply all of the numbers on a telephone's number pad?

What work can one never finish?

Solve the equation in the image by looking at the pattern closely.

In the image given, you can find several triangles. Can you count them all?

How many times can you subtract the number two from the number fifty?