Question of the Week 4: Rearranging Formula

The following question is taken from my website Diagnostic Questions. Here you will find 1000s of high quality maths questions, ideal for assessment for learning, which have been created and shared by maths teachers all over the world.

A nice little algebra question for you to try out on your students this week.

I find that rearranging formula is one area that quite a few students find difficulty. Algebra as a whole is a minefield of misconceptions, and rearranging formula tends to expose any errors in thinking and understanding that a student might have.

Let's have a look at what we might learn from student responses to this question:

suggests students have divided by two (incorrectly!) first. Perhaps they need to work on their order of operations, and their reading of algebraic expressions

implies that students have simply switched the two letters' positions and don't really understand what making the subject of a formula actually means

is the correct answer  And if you have used the question, or have any thoughts or comments about it – perhaps you would include a different incorrect answer – then please share your comments below. And please consider creating a question yourself on the website! 