diff --git a/subjects/manipulate-keys/README.md b/subjects/manipulate-keys/README.md
index 1b32ced0..19c764c9 100644
--- a/subjects/manipulate-keys/README.md
+++ b/subjects/manipulate-keys/README.md
@@ -10,6 +10,21 @@ Create 3 functions that works like the `.filter`, `.map` and `.reduce` array met
 - `mapKeys` changes the name of the items you have.
 - `reduceKeys` reducing you grocery cart.
 
+### Examples
+
+```js
+const nutrients = { carbohydrates: 12, protein: 20, fat: 5 }
+console.log(filterKeys(nutrients, (key) => /protein/.test(key)))
+// output :
+// { protein: 20 }
+console.log(mapKeys(nutrients, (k) => `-${k}`))
+// output :
+// { -carbohydrates: 12, -protein: 20, -fat: 5 }
+console.log(reduceKeys(nutrients, (acc, cr) =>acc.concat(', ', cr)))
+// output :
+// carbohydrates, protein, fat
+```
+
 ### Notions
 
 - [devdocs.io/javascript/global_objects/array/filter](https://devdocs.io/javascript/global_objects/array/filter)
diff --git a/subjects/manipulate-values/README.md b/subjects/manipulate-values/README.md
index c9897422..256df972 100644
--- a/subjects/manipulate-values/README.md
+++ b/subjects/manipulate-values/README.md
@@ -11,7 +11,25 @@ Create 3 functions that works like the `.filter`, `.map` and `.reduce` array met
 
 - `filterValues` filters the values of your grocery cart.
 - `mapValues` changes the values of your grocery cart.
-- `reduceValues` that will reduce your grocery cart.
+
+For the above function the callback function should accepts only the element in the arguments, this being the current element being processed.
+
+- `reduceValues` that will reduce your grocery cart. The callback function should accepts only the **accumulated value** and the **current value**.
+
+### Examples
+
+```js
+const nutrients = { carbohydrates: 12, protein: 20, fat: 5 }
+console.log(filterValues(nutrients, (nutrient) => nutrient <= 12))
+// output :
+// { carbohydrates: 12, fat: 5 }
+console.log(mapValues(nutrients, (v) => v+1))
+// output :
+// { carbohydrates: 13, protein: 21, fat: 6 }
+console.log(reduceValues(nutrients, (acc, cr) => acc + cr))
+// output :
+// 37
+```
 
 You will have a small database to help you with the groceries.
 
@@ -25,7 +43,7 @@ You will have a small database to help you with the groceries.
 
 ### Code provided
 
-> all code provided will be added to your solution and doesn't need to be submited.
+> all code provided will be added to your solution and doesn't need to be submitted.
 
 ```js
 // small database with nutrition facts, per 100 grams