To deal with the diversity of skill in class, as well as encouraging all students to practise transposition of formulae more, an online tutorial using the open source maths e-assessment platform Numbas has been developed in CIT. This online tutorial tool is intended to help the students to spend as much time as individually necessary on tasks of various difficulty, and hence master the skill at an individual pace. Click here to access this online tutorial tool and try it out. All you need to do is to give your students a link to it and give instructions on entering mathematical expressions (e.g. ^5 for a power of 5). The tool runs just as well on phones, tablets, and desktops. Click here for a tutorial on how to use Numbas.