Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

In a town, there are four houses located at different distances from each other. Following are the distances:

The third house is 60 meters apart from the first house.
The fourth house is 40 meters apart from the second house.
The third house is 10 meters nearer to the fourth house than it is to the second house.

Can you find out the distance between the fourth and the first house?

In the image below, can you find the value of an angle(y)

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

A cricket has 6 legs, a squirrel has 4 legs and a spider has 8 legs.

In a local zoo, it was found that the total number of legs is 612. Also, there are equal number of each of the above animals/insects.

Can you find out how many animals are there in the zoo?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

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

If "P" means "-", "Q" means "/", "R" means "+", and "S" means "*" then find the value of the following:

21 Q 7 R 9 S 10 P 13