Place a mathematical symbol between the numerals 5 and 9 in such a way that the resulting number is greater than 5 but smaller than 9.

A red house is made out of red bricks. A yellow house is made out of yellow bricks. And, a blue house is made out of blue bricks. So, what is a greenhouse made of?

Prove that twice of ten is the same as twice of eleven.

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

What kind of tree can you carry in your hand?

You have to put a letter on the following to make it a meaningful word. The only challenge is that you can't use 'E'.

S E Q U E N C _

Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the bridge?

I travel all around the world but always stay in the corner. What am I?

What do you get if you add 2 to 100 four times?

My thunder comes before the lightning; my lightning comes before clouds; my rain dries all the land it touches. What am I?