Class News

Math
I have 5 coloured discs in a pile as shown.
I take the top two discs and put them on the bottom (with the red disc still on top of the blue disc). Then I again take the top two discs and put them on the bottom.
If I do this until I have made a total of 21 moves, which disc will be on the bottom?
(Race your answers to Ms Brennan tomorrow!)