1.1. A training track for cyclists is in the shape of a circle made up of several lanes.

The shortest, inner lane has a radius of 10 m, with each lane working outwards having a radius 4 m greater than the previous lane.

During a training session a cyclist is expected to complete two laps of each lane, starting with the inner lane, before moving onto the next one.

You may assume that the lap distance of each lane is the circumference of the circle with the radius indicated above.

Show that the lap distances of each lane form an increasing arithmetic sequence and state the first term and common difference.

1.2. Find the distance completed by a cyclist during a training session and using the first six lanes only.

1.3. There is a total of 10 lanes on the training track.

If a cyclist wishes to travel a total distance more than twice round each lane, they may continue as many laps around the outside lane as necessary.

A more advanced cyclist wants to travel a distance of at least 6 km during their session. How many laps of the outside lane the cyclist will need to do in total?