Everybody has an excuse for not working out and being busy is one of the most popular.
Let me shoot that down today with a quick and demanding workout that will help you build stamina and power at the same time.
Warm-up: 100 Jumping Jacks (~2 min)
10 pushups, 10 prisoner squats, 10 crunches (note: no rest between sets)
9 pushups, 9 prisoner squats, 9 crunches
and so on till you do one of each. (~8 minutes)
Cool down: 50 jumping jacks and various stretches (~5 minutes)
You end up doing a total of 55 reps of each exercise and will get a hell of a cardio workout too. The best part is, you need no equipment!
Make this workout more challenging by adding plyo push-ups and squats or increasing the starting point to 12 or even 15.