Lines and spheres

What code goes into the question mark?

You can check your solution at here

How many rhombuses?

In Mathematics, a Rhombus is a figure consisting of 4 lines, all of the same size, and with opposing sides parallel.
Thus:

How many rhombuses do you count in this figure?

You can check your solution at here

Please try to solve the puzzles on your own: your self confidence will grow. You are welcome to remark on the puzzles, and I love it when you comment variations, state wether they are too easy or too difficult, or simply your solution times. Please do not state the soultions – it spoils the fun for others. I usually make the solution available after one or two weeks through a link, which allows readers to check the solution without the temptation to scroll down a few lines before having a go at it themselves.

A prime maze

Mazes are very old and very diverse. I hope to write about mazes in eneral another time, but here is one variation.

Go from 1 the upper left corner to the bottom right corner with the following rules:
1) When you move from one square to the next, add the number in between
2) Every new number must be a prime number

For those of you, a prime number is a number of 2 or more which can only be divided by 1 and by itself. Thus 2, 3, 5 and so on are prime numbers, but 4, 6 and 9 are not.

I found this type of puzzle in one of the old Dutch math olympiads.

You can check your solution at here

Please try to solve the puzzles on your own: your self confidence will grow. You are welcome to remark on the puzzles, and I love it when you comment variations, state wether they are too easy or too difficult, or simply your solution times. Please do not state the soultions – it spoils the fun for others. I usually make the solution available after one or two weeks through a link, which allows readers to check the solution without the temptation to scroll down a few lines before having a go at it themselves.

Color grid (1)

What number goes into the cell with the question mark?

1) Color grid^*

You can check your solution at here

Please try to solve the puzzles on your own: your self confidence will grow. You are welcome to remark on the puzzles, and I love it when you comment variations, state wether they are too easy or too difficult, or simply your solution times. Please do not state the soultions – it spoils the fun for others. I usually make the solution available after one or two weeks through a link, which allows readers to check the solution without the temptation to scroll down a few lines before having a go at it themselves.

You can find more puzzles of this type in one of our free or paid upcoming e-books on Logic puzzles.