diff --git a/docs/source/pythonapi/examples/tally-arithmetic.ipynb b/docs/source/pythonapi/examples/tally-arithmetic.ipynb
index e68aa36d6..64681b424 100644
--- a/docs/source/pythonapi/examples/tally-arithmetic.ipynb
+++ b/docs/source/pythonapi/examples/tally-arithmetic.ipynb
@@ -725,7 +725,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "We have a tally of the total fission rate and the total absorption rate, so we can calculating k-infinity as:\n",
+    "We have a tally of the total fission rate and the total absorption rate, so we can calculate k-infinity as:\n",
     "$$k_\\infty = \\frac{\\nu \\Sigma_f \\phi}{\\Sigma_a \\phi}$$"
    ]
   },