Count the number of triangles in the below picture?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

If a zookeeper had 100 pairs of animals in her zoo, and two pairs of babies are born for each one of the original animals, then (sadly) 23 animals don’t survive, how many animals do you have left in total?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

Take away my first letter, then take away my second letter. Then take away the rest of my letters, yet I remain the same. What am I?

Which is the smallest number that you can write using all the vowels exactly once?

How many words can a pen with half refill write?

Things are just as they seem, right? Well, check again.
Can you count the number of tigers in this picture ?

Alex is stranded on an island covered in forest.
One day, when the wind is blowing from the west, lightning strikes the west end of the island and sets fire to the forest. The fire is very violent, burning everything in its path, and without intervention the fire will burn the whole island, killing the man in the process.

There are cliffs around the island, so he cannot jump off.

How can the Alex survive the fire? (There are no buckets or any other means to put out the fire)

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