In a school, there are four subjects. Seventy percent of students study English, seventy five percent of students study Science, eighty five percent of students study Mathematics and eighty percent of students study Spanish.

Can you calculate the percentage of students that study all four subjects?

A blonde put eyeliner on her head. Why?

Count the number of triangles in the given picture.

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

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

A father's child, a mother's child, yet no one's son.

Who am I?

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

I am white when I am dirty, and black when I am clean. What am I?

These types of puzzles are known as charades. What you have to do is find two words that are referred to in the first stanza and the second stanza and put them together to form the third word in the third stanza.

Just for example, if my first refers to 'off' and my second refers to 'ice', then my whole will be office.

My first is present - future's past -
A time in which your lot is cast.

My second is my first of space
Defining people's present place.

My whole describes a lack of site -
A place without length, breadth, or height.

Can you find the odd number in the following?

2716, 4135, 5321 and 7145