Here are a list of workout I usually do.
I usually vary my cardio exercise so that it wont get boring and to prevent my body to adapt to it.
i ) Treadmill 40 minutes at 7.5 kmh or
ii) Treadmill 20 minutes at 9 kmh or
iii) Treadmill 20 minutes interval of 11kmh and 5.5kmh
iv) Swimming 40 minutes - 1 hour mix of freestyle and breast stroke.
v) Elliptical trainer at medium intensity for 30 minutes
vi) Bicycle machine for 30 minutes at medium resistance. Try to hit 15km -20 kmh
vii) Walking on treadmill with 15% incline at 3.5-5.5kmh