QTS Numeracy Skills Test - Mental Arithmetic Tips and Tricks
https://www.youtube.com/watch?v=VM6zkJ-_RRU

Free Numeracy course:
https://www.futurelearn.com/courses/numeracy-skills

Resources (with activities)

5 minute Numeracy Guide:
http://library.bcu.ac.uk/learner/Numeracy.pdf

English and Maths for Adults:
http://www.bbc.co.uk/skillswise/maths