Aisha is training for a marathon by running on a track. The length of the track is 400 metres.
On the first day of her training, she runs 15 laps of the track.
Each day, she increases the number of laps she runs by 3.
Write down an expression for the number of laps Aisha will run on her n n\,nth day of training.
Aisha's target is to run at least 42,000 metres (42 km) in a single day. Determine the minimum number of days she will need to train to reach this target.
A sport scientist claims that by the time Aisha reaches her target day, she will have run a collective total of over 850,000 metres across all training days. Determine if the sport scientist is correct.