Grow or Shrink? Mastering Percentage Change

A pair of trainers cost £80 last month. This month they cost £100. Something has changed — but by how much, really? You might say '£20 more', and you'd be right. But £20 means something very different if the original price was £80 versus if it was £800. That's why we use percentage change: it tells us how big a change is relative to where we started. Before we dive in, try this quick retrieval check.