Two tasks based on converting between standard form and ordinary form. As ever - plenty of practice without repetition. In brief: The code breaker task is designed as a practice task giving students plenty of opportunities to convert between standard and ordinary form. The apply task uses real examples of numbers in standard form, as well as interpreting calculator displays given in standard form. Included: Code Breaker Worksheet (Practice Task) Code Breaker Answers Apply Task Worksheet Apply Task Answers Skills covered include: Converting from standard form to ordinary form Converting from ordinary form to standard form Correcting numbers incorrectly written in standard form Using and interpreting answers given on a calculator (eg 20!) The two tasks can be used to differentiate easily - have the students who are more competent move straight onto the apply task. Separate answer sheets are included, I normally display this at the back of the room and have students check their work as they see fit.