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

John and Jill are madly in love with each other. To remind Jill of his pure love, John wants to send her a ring by post but in their country where burglary is quite prominent, any package that is not locked comes under the risk of being stolen for the contents.

John and Jill possess many padlocks but neither one of them has the other key.

Can you find a way John can send the ring to Jill safely?

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

I am green and found in the forest and have needles instead of leaves. What am I?
Hint 1: It can be used for Christmas decorations.
Hint 2: I have a strong, scent that is used in air fresheners.

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?

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?

By removing one matchstick and adding one matchstick, can you convert the word "ZOO" to an animal name?

Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not-rounded numerals equals 24.

What is the coolest letter in the alphabet?