Montana

How it works: Choose one of four answers to solve each sum. Every correct answer moves your climber one step up the mountain. Answer ten sums correctly to reach the summit; the climber then glides back down on skis. Choose easy, medium or hard before you start. Each question gives you 10, 7 or 4 seconds, depending on the level.

Score and best result: Each correct answer earns 10 base points plus 1 bonus point for every second left on that question's countdown. A correct answer can earn up to 20, 17 or 14 points, depending on the level. Wrong answers and time-outs do not move you up or earn points; a new sum appears. Your best score for each level is saved in this browser. Scores reaching the top five can be submitted to the online leaderboard. When scores are equal, the faster total time ranks higher.