diff --git a/solutions/day-01/functions.js b/solutions/day-01/functions.js
index 531a17d..c593976 100644
--- a/solutions/day-01/functions.js
+++ b/solutions/day-01/functions.js
@@ -35,5 +35,76 @@ function sum(arr) {
 }
 
 function sumAllNums() {
-    console.log(arguments)
+    let sum = 0
+    for (let i = 0; i < arguments.length; i++){
+        sum += arguments[i]
+    }
+    return sum
+}
+
+console.log(sumAllNums(15, 20, 30, 25, 10, 33, 40))  // 173
+
+// arrow functions are shorter syntax (that's it)
+// but also there is no arguments inside this type of function scope...
+// also there is no usual "this" object binding
+// but instead the this keyword always representd the object that defined the arrow function
+// usually, this represents the object that calls the function
+// but with arrow functions this represents the owner of the function
+hello = () => "hello arrow function!"
+
+// or it can pass variables
+
+helloPerson = (val) => "hello " + val
+
+// can even skip parenthesis
+
+helloSimplified = val => "Hello " + val 
+
+// sum all nums arrow function
+const sumAllNumsArrow = (...args) => {
+    let sum = 0
+    for (const element of args) {
+        sum += element
+    }
+    return sum
+}
+
+console.log("sum all nums with arrow function: " + sumAllNumsArrow(1, 2, 3, 4, 5, 6, 7))
+
+const changeToUpper = (arr) => {
+    const newArr = []
+    for (const element of arr) {
+        newArr.push(element.toUpperCase())
+    }
+    return newArr
+}
+
+console.log(changeToUpper(countries))
+
+// default params, arrow function
+const printNameFull = (firstName = 'Ivy', lastName = 'Graham') => `${firstName} ${lastName}`
+console.log(printNameFull('Derrek', 'Gass'))
+console.log(printNameFull())
+
+function calcAge(birthYear, currentYear = 2020) {
+    let age = currentYear - birthYear
+    return age
+}
+
+console.log('Age: ', calcAge(1990))
+
+function weightOfObject(mass, gravity = 9.81) {
+    let weight = mass * gravity + ' N'
+    return weight
+}
+
+console.log('Weight of object in Newtons: ', weightOfObject(110))
+console.log('Weight of object in Newtons: ', weightOfObject(150))
+console.log('Weight of object in Newtons (on Moon): ', weightOfObject(110, 1.62))
+
+const greetings = (name = 'Derrek') => {
+    let message = name + ', welcome to 30 days of JavaScript!'
+    return message
 }
+console.log(greetings())
+console.log(greetings('Ivy'))