1 Hour or less
It is not advisable to walk on a treadmill with a broken rib as it can cause further discomfort and delay the healing process. It is best to rest and allow your rib to heal properly before engaging in any physical activity.
Does not really matter, I normally walk first and then Bike
atleast 1 hr is important
All treadmill would give you approximately the same type of cardio workout. To increase your workout, you may want to choose a treadmill that allows you to walk fast or to walk "uphill".
A treadmill.
1000000000 hours if you walk
There are 1,000 metres in a kilometre.Therefore, in 1.5 kilometres, there are 1,500 metres.
Grout should dry for at least 24 hours before it is safe to walk on.
You walk
540/4 = 132.5 hours
If you want to work with your laptop while exercising it would be best to buy a treadmill desk workstation. There is a nice treadmill standing adjustable desk at treadmilldeskinc.com. You can walk while you work on your laptop.
1 hour if swimming, 30 min for any thing else.