Double Under Warm-up
Leo practices jump rope as part of his warm-up routine for basketball. There are three different sets he practices. Set A is 15 seconds long, when he jumps at the rate of 21 double unders per 9 seconds. Set B is 30 seconds long, when he jumps at the rate of 22 double unders per 10 seconds. Set C is 1 minute long, when he jumps at the rate of 23 double unders per 12 seconds. The warm-up period is 10 minutes, starting from the beginning of the first set. Leo would add a set to the remaining seconds if and only if completing the set doesn't make him go beyond the 10-minute period. The warm-up follows the rules below:
- The adjacent sets must be different;
- Leo has to practice all three sets during the warm-up;
- The resting time between two adjacent sets is the sum of duration of the two adjacent sets.
Previously, Dr. Hong arranged the warm-up plan to minimize the number of sets. This week, Dr. Hong changed the plan to maximize the number of double unders Leo jumps. How many extra double unders in a warm-up does Leo have to jump this week?