If it took eight men ten hours to build a wall, how long would it take four men to build it?

How many triangles are there on the puzzle below?

A man lives on the fifteenth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator, or if it was raining that day, he goes back to his floor directly. Otherwise, he goes to the tenth floor and walks up five flights of stairs to his apartment. Can you explain why he does this?

If Japan and Panama decided to merge into a single country, probably people will name it Japanama.

Can you think of two more such country's unions that could produce similar names like Japanama by overlapping their three letters?

How many times do a clock's hands overlap in a day ?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

What is more useful when it is broken?

What has hands, but can’t clap?

Can you find the dog hidden in a group of pandas?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?