My class loved this Enigma machine themed code breaking investigation. It requires pupils to be able to simplify fractions, compare fractions changing the denominator and adding fractions with the same and different denominators. A fun way to assess learning and links well to your history lesson if you're doing WW2. I've listed this as a 1 hour lesson but you could split each word of the code into a different lesson working on a different fraction concept. Concepts covered are:
Equivalent Fracti