diff --git a/docs/Assignments/week_9_input_devices/input_devices.md b/docs/Assignments/week_9_input_devices/input_devices.md
index bfc80d1..d4f567b 100644
--- a/docs/Assignments/week_9_input_devices/input_devices.md
+++ b/docs/Assignments/week_9_input_devices/input_devices.md
@@ -71,7 +71,7 @@ Something else I found out is that if you order 5 boards you get a big discount
 This week I learned how voltage dividers worked and I also struggled a lot with them. A voltage divider is better for splitting voltage instead of creating a voltage drop using a single resistor. Because you don't have to know how much current is flowing. Instead you can divide the voltage between 2 lanes. This way you can receive an 5v analog signal on a esp without frying it.
 
 ![alt text](image321.jpg)
-I found a lot of helpfull explanation on [this website](https://www.khanacademy.org/science/electrical-engineering/ee-circuit-analysis-topic/ee-resistor-circuits/a/ee-voltage-divider).
+I found a lot of helpful explanation on [this website](https://www.khanacademy.org/science/electrical-engineering/ee-circuit-analysis-topic/ee-resistor-circuits/a/ee-voltage-divider).
 
 
 ## The drone control board