A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

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 _

They came out at night, without being called.
They lost at day, without being stolen.
Who are they?

What word begins and ends with an E, but has only one letter?

What brings you down but never up?

What is black when you buy it, red when you use it, and gray when you throw it away?

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?

Three fair coins are tossed in the air and they land with heads up. Can you calculate the chances that when they are tossed again, two coins will again land with heads up?

Replace the question mark with the correct number in the below-given picture?

Move four matchsticks to the below square to form three squares?