diff --git a/exercises/robot_arm/problem.fr.md b/exercises/robot_arm/problem.fr.md
index 18f7308..f47f07c 100644
--- a/exercises/robot_arm/problem.fr.md
+++ b/exercises/robot_arm/problem.fr.md
@@ -39,13 +39,11 @@ Utilise un potentiomètre (potard) pour controller la position d'un servomoteur.
 ## Documentation
 
 - Sensor - https://github.com/rwaldron/johnny-five/wiki/Sensor
-- Fn - https://github.com/rwaldron/johnny-five/blob/master/lib/fn.js
 
 ## Conseils
 
 - Un potard est un autre cas d'utilisation de l'objet 'Sensor'...
 - Un potard a produit des valeurs dans une plage allant de 0 a 1023.
 - Un servomoteur peut généralement étre orienté dans un angle de 0 a 180°.
-- `five.Fn.map` peut étre utiliser pour normaliser les valeur du potard (0 - 1023) en angles pour le servomoteur (0 - 179).
 
-* * *
\ No newline at end of file
+* * *
diff --git a/exercises/robot_arm/problem.ja.md b/exercises/robot_arm/problem.ja.md
index 63f0089..51e2ee6 100644
--- a/exercises/robot_arm/problem.ja.md
+++ b/exercises/robot_arm/problem.ja.md
@@ -40,13 +40,11 @@ GND  o---.------/\/\/------.
 ## ドキュメント
 
 - Sensor - https://github.com/rwaldron/johnny-five/wiki/Sensor
-- Fn - https://github.com/rwaldron/johnny-five/blob/master/lib/fn.js
 
 ## ヒント
 
 - ポテンショメータは、センサーオブジェクトの別のユースケースです。
 - 0〜1023の間の入力値を生成します。
 - サーボは通常0〜179度の角度を動くことができます。
-- `five.Fn.mapメソッド`はポテンショメータの値(0~1023)をサーボの角度(0~179)にマッピングすることができます。
 
 ---
diff --git a/exercises/robot_arm/problem.md b/exercises/robot_arm/problem.md
index 126af03..eccca42 100644
--- a/exercises/robot_arm/problem.md
+++ b/exercises/robot_arm/problem.md
@@ -40,13 +40,11 @@ GND  o---.------/\/\/------.
 ## Docs
 
 - Sensor - https://github.com/rwaldron/johnny-five/wiki/Sensor
-- Fn - https://github.com/rwaldron/johnny-five/blob/master/lib/fn.js
 
 ## Hints
 
 - A potentiometer is another use case for the Sensor object...
 - A pot produces input values between 0 and 1023.
 - A servo can typically be moved between 0 and 179 degrees.
-- `five.Fn.map` can map the pot values (0 - 1023) to servo angles (0 - 179).
 
 ---
diff --git a/exercises/robot_arm/solution/solution.js b/exercises/robot_arm/solution/solution.js
index 4daa62d..ec5c125 100644
--- a/exercises/robot_arm/solution/solution.js
+++ b/exercises/robot_arm/solution/solution.js
@@ -5,21 +5,7 @@ board.on('ready', function () {
   var servo = new five.Servo(9)
   var pot = new five.Sensor('A2')
 
-  pot.on('change', function () {
-    var position = five.Fn.map(this.value,
-      0, 1023,
-      0,  179
-    )
-
-    servo.to(position)
-  })
-
-  // Alternatively, sensor provides a `scale` method as an alias to Fn.map
-  /*
-  pot.scale(0, 179).on('change', function () {
-
-    // `this.value` will reflect a scaling from 0-1023 to 0-179
+  pot.scaleTo(0,179).on('change', function () {
     servo.to(this.value)
   })
-  */
 })