The first 15min workout

Simplicity is the best. And that is exactly what we will do. We'll start off simple because really, the simpler the exercise the better. So what is on the menu? Push-ups. Simple, but effective. Push-ups works a whole range of muscles. Your biceps and triceps (thats your arms), your chest (thats your uh chest...hah), your back muscles, your whole abdominal (stomach area and sides) and your hamstrings. One workout, and more than 6 major muscles worked. Not a bad deal no? And honestly your work out would probably take less than 15mins. Lets run through the workout step-by-step.

1) Stretch
The first thing we need to do is warm up our muscles by stretching. 1 MAIN stretch we have to do.
Place your hand on a wall, straighten your arm, and push forward. This stretches your chest. Hold the position for 10x3 seconds and do for both arms.

2) The workout: Push-ups

As I said, this workout is easy but works a lot of muscles. So the basic push-up we all know.

Body straight, go down till your arms have bent at least 90 degrees. Now HOLD at the down position for 1 second, then come back up.
How many should you do?
For beginners:
Do 3 sets of push-ups. For each set, do till exhaustion (do it until you cant do anymore!) Now for the first set you might be able to do 13~the second set 7~and the third set just 2. Its perfectly fine. As you do this exercise daily, you will find that this number will increase.
For more advanced groups:
Set a target of how many push-ups you want to do per day. 100-300 push-ups is a good number to work with. Now split this number up into challenging but yet manageable sets. I currently do 20 per set.
Now if you are not able to do a regular push-up~or if you are on your 18th set of 20 push-ups but you are hurtingggg~Go into the knee position and continue on. DO NOT STOP EVEN IF IT HURTS.

When you are doing a knee push-up, you are still lifting about 50% of your body weight! It feels alot easier, but you are still getting an awesome workout (yes contrary to popular belief, it aint a sissy push-up). So if you are totally blown out on your last set, just go to this position. You are overloading your muscles (this is a good thing) and you are still getting a good workout.
For those who are not able to do a single regular push-up, do this knee variation. Instead, go down to the count of 10, and come up to the count of 10. Again, do 3 sets till exhaustion.
3) Do the same stretches as a cool down
your muscles only grow if they are stretched after they are worked! this is of vital importance.

Remember the key to anything is consistency. Keep up with this everyday and you will see spectacular results after awhile.
And so cheers! This is your first 15min (or less) workout.