Replace the question mark with the correct number below.

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

Andrew sees a very rare bird named "Ruppell's vulture". Soon Andrew was dead. Can you explain the mystery, Mr. Sherlock?

Rectify the following equality 101 - 102 = 1 by moving just one digit.

I have two sand hourglasses:
1. A 7 minute one and
2. An 11-minute one.

Using just these 2 sand hourglasses, how can I measure time as 15 minutes?

Jack was having a candle light dinner with his girlfriend. Suddenly a cold gush of wind entered through the open window and three of the ten candles were extinguished. Assuming that none of the other candles were extinguished.

How many candles are they left with in the end ?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

What does the below image rebus riddle means ?

I have an eye but still cannot see.

Who am I?

It has a long neck, A name of a bird, Feeds on cargo of ships, It's not alive,

What is it?