Straight line graphs

On my way to work I picked up a voicemail from daughter # 1's school asking why she wasn't at school. She had left home for school with her mates at 8.15. When I called school, they told me that it was a mistake and she had been located ( she was doing some reporting for the BBC).
It was another cold day today and much colder on the way home from work. No sign of spring yet !
After dinner I helped daughter #2 with her maths homework (straight line graphs).