Before you can register, you must answer 3 simple questions. All answers are numbers. If the answer is integer, simply type it in the corresponding field. A fraction must be typed in its simple irreducible form, i.e. 5/2 (neither 2.5, nor 2 1/2).

What is next: 1 3 9 27 81 ...?

How many natural numbers less than 1000 are not divisible by 5 and 7?

A brick weighs 1 Kg and half a brick. How much does the brick weigh?