diff --git a/slides/maths.en.md b/slides/maths.en.md
index c8734ce..ebc8a92 100644
--- a/slides/maths.en.md
+++ b/slides/maths.en.md
@@ -93,7 +93,7 @@ Code up the following formulas in the file `exercises/maths/math-formulas.tex`.
 
 | Meaning | Result |
 |---------|--------|
-| Gravitational acceleration | $9,81\,\frac{m}{s^2}$  |
+| Gravitational acceleration | $9.81\,\frac{m}{s^2}$  |
 | Formula to solve quadratic equations | $x_{1,2} = - \frac{p}{2} \pm \sqrt{\left(\frac{p}{2}\right)^2 - q}$ |
 | Another formula to solve quadratic equations | $x_{1,2} = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$ |
 | Catalan numbers | $C_n = \frac{1}{n+1} {2n \choose n} = \frac{(2n)!}{(n+1)!n!}$ |