SIKORE can help everyone to improve his mental arithmetic skills. You can easily generate free sheets with arithmetic problems for printing. Or solve the problems online with your browser. The difficulty is freely configurable.
 Difficulty: Level 1: To 10, just plus/minus Level 2: To 19, just plus/minus, no carrying Level 3: To 20, just plus/minus Level 4: To 99, just plus/minus, no carrying Level 5: To 100, just plus/minus Level 6: To 100, multiplied by 10 Level 7: To 200, just plus/minus Level 8: To 200, multiplied by 10 Level 9: To 250, just plus/minus Level 10: To 250, multiplied by 15 Level 11: To 500, just plus/minus Level 12: To 500, multiplied by 10 Level 13: To 500, multiplied by 20 Level 14: To 1000, just plus/minus Level 15: To 1000, multiplied by 10 Level 16: To 1000, multiplied by 20 Level 17: To 1000, multiplied by 30 Level 18: To 2000, just plus/minus Level 19: To 2000, multiplied by 20 Level 20: To 2000, multiplied by 30 Level 21: To 2000, multiplied by 40 Level 22: To 5000, just plus/minus Level 23: To 5000, multiplied by 30 Level 24: To 5000, multiplied by 50 Level 25: To 5000, multiplied by 70 Level 26: To 10000 just plus/minus Level 27: To 10000 multiplied by 30 Level 28: To 10000 multiplied by 50 Level 29: To 10000 multiplied by 100 Level 30: To 100000, just plus/minus Level 31: To 100000, multiplied by 50 Level 32: To 100000, multiplied by 100 Level 33: To 100000, multiplied by 300 Level 34: To 500000, just plus/minus Level 35: To 500000, multiplied by 100 Level 36: To 500000, multiplied by 300 Level 37: To 500000, multiplied by 500 Level 38: To 999999, just plus/minus Level 39: To 999999, multiplied by 999 user-defined Advanced: Pick one of the above, preconfigured difficulties or click here to show further options for configuration. Sheet: Generate sheet Generate one sheet with problems and one with results for printing. The sheets open in two new tabs. Attention: Deactivate the popup-blocker. SIKORE Live: Calculate now Create one chain and solve it online now.

## How it works

• Every chain with problems spans several lines. At the end of a line the intermediate result is copied to the beginning of the next line and used for the further calculations.
• There are five chains on a sheet, e.g. one for every day of the (school-)week.
• Use it in many ways: homework, exercise at school, with time limit, hall of fames, ...

## Miscellaneous

SIKORE is my hobby. You may use it free of charge. A downloadable version (just for usage on computers without internet access) is available on request. Feedback is always welcome (just write to mich). Donations are welcome, too. Via PayPal:
By the way, the word SIKORE is an abbreviation of Sicher Kopfrechnen which means reliable mental arithmetic.