This is a simple test for **mental arithmetic**. Train your brain with mental calculation and compare your speed with others! There are few simple rules:

- Do NOT use pen and paper or a calculator. Do not consult others.
- In order to complete the test you should reach 15/15 points.
- For every correct answer you get +1 point, for each wrong answer you get -1 point.
- The time took to complete this mental arithmetic test is part of the final score.
- There are three difficulty levels in this test. Choose one of them to start.
- Once "I'm ready! Let's go!" is clicked, the timer starts and you should reach 15/15 points as fast as possible.
- You can press "Enter" on your keyboard to send the answer to save time.
- Good luck!