Created arithmetic operators concept, as per #1049

concepts/arithmetic-operators/.meta/config.json

@@ -0,0 +1,5 @@
+{
+  "authors": ["JaPatGitHub"],
+  "contributors": [],
+  "blurb": "Javascript has 6 different operators to perform basic arithmetic operations on numbers. Additionally there is a matching shorthand assignment operator for each of those."
+}

concepts/arithmetic-operators/about.md

@@ -0,0 +1,84 @@
+# About
+
+## Arithmetic Operators
+
+Javascript provides 6 different operators to perform basic arithmetic operations on numbers.
+
+- `+`: The addition operator is used to find sum of numbers.
+
+  ```javascript
+  1 + 2; // => 3
+  2.5 + 3.9; // => 6.5
+  ```
+
+- `-`: The subtraction operator is used to find the difference between two numbers
+
+  ```javascript
+  19 - 2; // => 17
+  7.4 - 1.2; // => 1.5
+  ```
+
+- `*`: The multiplication operator is used to find the product of two numbers two numbers
+
+  ```javascript
+  7 * 5; // => 35
+  9.2 * 6.3; // => 57.959999999999994
+  ```
+
+- `/`: The division operator is used to divide two numbers.
+  Since JavaScript numbers are always floating point numbers, there is no integer division.
+
+  ```javascript
+  8 / 2; // => 4
+  25 / 3; // => 8.333333333333334
+  ```
+
+- `%`: The remainder operator is used to find the remainder of a division performed.
+
+  ```javascript
+  40 % 4; // => 0
+  11 % 4; // => 3
+  -11 % 4; // => -3
+  ```
+
+- `**`: The exponentiation operator is used to raise a number to a power.
+  It is the equivalent of using [`Math.pow()`][mdn-math-pow]
+
+  ```javascript
+  4 ** 3; // => 62
+  4 ** 1 / 2; // => 2
+  ```
+
+## Order of Operations
+
+When using multiple operators in a line, JavaScript follows an order of precedence as shown in [this precedence table][mdn-operator-precedence].
+To simplify it to our context, JavaScript uses the PEDMAS (Parentheses, Exponents, Division/Multiplication, Addition/Subtraction) rule we've leant in elementary math classes.
+
+<!-- prettier-ignore-start -->
+```javascript
+const result = 3 ** 3 + 9 * 4 / (3 - 1);
+// => 3 ** 3 + 9 * 4/2
+// => 27 + 9 * 4/2
+// => 27 + 18
+// => 45
+```
+<!-- prettier-ignore-end -->
+
+## Shorthand Assignment Operators
+
+Shorthand assignment operators are a shorter way of writing code conducting arithmetic operations on a variable, and assigning the new value to the same variable.
+For example, consider two variables `x` and `y`.
+Then, `x += y` is same as `x = x + y`.
+Often, this is used with a number instead of a variable `y`.
+The 5 other operations can also be conducted in a similar style.
+
+```javascript
+let x = 5;
+x += 25; // x is now 30
+
+let y = 31;
+y %= 3; // y is now 1
+```
+
+[mdn-math-pow]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/pow
+[mdn-operator-precedence]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence#table

concepts/arithmetic-operators/introduction.md

@@ -0,0 +1,62 @@
+# Introduction
+
+## Arithmetic Operators
+
+Javascript provides 6 different operators to perform basic arithmetic operations on numbers.
+
+- `+`: The addition operator is used to find sum of numbers.
+- `-`: The subtraction operator is used to find the difference between two numbers
+- `*`: The multiplication operator is used to find the product of two numbers.
+- `/`: The division operator is used to divide two numbers.
+
+```javascript
+2 - 1.5; //=> 0.5
+19 / 2; //=> 9.5
+```
+
+- `%`: The remainder operator is used to find the remainder of a division performed.
+
+  ```javascript
+  40 % 4; // => 0
+  -11 % 4; // => -3
+  ```
+
+- `**`: The exponentiation operator is used to raise a number to a power.
+
+  ```javascript
+  4 ** 3; // => 62
+  4 ** 1 / 2; // => 2
+  ```
+
+## Order of Operations
+
+When using multiple operators in a line, JavaScript follows an order of precedence as shown in [this precedence table][mdn-operator-precedence].
+To simplify it to our context, JavaScript uses the PEDMAS (Parentheses, Exponents, Division/Multiplication, Addition/Subtraction) rule we've leant in elementary math classes.
+
+<!-- prettier-ignore-start -->
+```javascript
+const result = 3 ** 3 + 9 * 4 / (3 - 1);
+// => 3 ** 3 + 9 * 4/2
+// => 27 + 9 * 4/2
+// => 27 + 18
+// => 45
+```
+<!-- prettier-ignore-end -->
+
+## Shorthand Assignment Operators
+
+Shorthand assignment operators are a shorter way of writing code conducting arithmetic operations on a variable, and assigning the new value to the same variable.
+For example, consider two variables `x` and `y`.
+Then, `x += y` is same as `x = x + y`.
+Often, this is used with a number instead of a variable `y`.
+The 5 other operations can also be conducted in a similar style.
+
+```javascript
+let x = 5;
+x += 25; // x is now 30
+
+let y = 31;
+y %= 3; // y is now 1
+```
+
+[mdn-operator-precedence]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence#table

concepts/arithmetic-operators/links.json

@@ -0,0 +1,14 @@
+[
+  {
+    "url": "https://javascript.info/operators#maths",
+    "description": "javascript.info: Arithmetic Operators"
+  },
+  {
+    "url": "https://javascript.info/operators#modify-in-place",
+    "description": "javascript.info: Shorthand Assignment Operators"
+  },
+  {
+    "url": "https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence",
+    "description": "MDN: Operator Precedence"
+  }
+]

config.json

@@ -46,7 +46,7 @@
         "slug": "freelancer-rates",
         "name": "Freelancer Rates",
         "uuid": "0aff2fa7-55ea-47e9-af4a-78927d916baf",
-        "concepts": ["numbers"],
+        "concepts": ["numbers", "arithmetic-operators"],
         "prerequisites": ["basics"],
         "status": "beta"
       },
@@ -1626,6 +1626,11 @@
     ]
   },
   "concepts": [
+    {
+      "uuid": "82329ca4-62a6-4df4-be44-73cecc21e1b8",
+      "slug": "arithmetic-operators",
+      "name": "Arithmetic Operators"
+    },
     {
       "uuid": "e1b15569-387c-4833-8c3b-9a94e0ee1583",
       "slug": "array-analysis",

exercises/concept/freelancer-rates/.docs/instructions.md

@@ -7,7 +7,7 @@ We first establish a few rules between the freelancer and the project manager:
 - The daily rate is 8 times the hourly rate;
 - A month has 22 billable days.
 
-If the freelancer bills the project manager per month, there is a discount applied. This can be handy if the project manager has a fixed budget.
+If the freelancer bills the project manager per month or more, there is a discount applied. This can be handy if the project manager has a fixed budget.
 
 Discounts are modeled as fractional numbers (percentage) between `0.0` (`0%`, no discount) and `0.90` (`90%`, maximum discount).
 

exercises/concept/freelancer-rates/.docs/introduction.md

@@ -1,5 +1,7 @@
 # Introduction
 
+## Numbers
+
 Many programming languages have specific numeric types to represent different types of numbers, but JavaScript only has two:
 
 - `number`: a numeric data type in the double-precision 64-bit floating point format (IEEE 754).
@@ -9,3 +11,64 @@ Many programming languages have specific numeric types to represent different ty
 
 If you require arbitrary precision or work with extremely large numbers, use the `bigint` type.
 Otherwise, the `number` type is likely the better option.
+
+## Arithmetic Operators
+
+Javascript provides 6 different operators to perform basic arithmetic operations on numbers.
+
+- `+`: The addition operator is used to find sum of numbers.
+- `-`: The subtraction operator is used to find the difference between two numbers
+- `*`: The multiplication operator is used to find the product of two numbers.
+- `/`: The division operator is used to divide two numbers.
+
+```javascript
+2 - 1.5; //=> 0.5
+19 / 2; //=> 9.5
+```
+
+- `%`: The remainder operator is used to find the remainder of a division performed.
+
+  ```javascript
+  40 % 4; // => 0
+  -11 % 4; // => -3
+  ```
+
+- `**`: The exponentiation operator is used to raise a number to a power.
+
+  ```javascript
+  4 ** 3; // => 62
+  4 ** 1 / 2; // => 2
+  ```
+
+### Order of Operations
+
+When using multiple operators in a line, JavaScript follows an order of precedence as shown in [this precedence table][mdn-operator-precedence].
+To simplify it to our context, JavaScript uses the PEDMAS (Parentheses, Exponents, Division/Multiplication, Addition/Subtraction) rule we've leant in elementary math classes.
+
+<!-- prettier-ignore-start -->
+```javascript
+const result = 3 ** 3 + 9 * 4 / (3 - 1);
+// => 3 ** 3 + 9 * 4/2
+// => 27 + 9 * 4/2
+// => 27 + 18
+// => 45
+```
+<!-- prettier-ignore-end -->
+
+### Shorthand Assignment Operators
+
+Shorthand assignment operators are a shorter way of writing code conducting arithmetic operations on a variable, and assigning the new value to the same variable.
+For example, consider two variables `x` and `y`.
+Then, `x += y` is same as `x = x + y`.
+Often, this is used with a number instead of a variable `y`.
+The 5 other operations can also be conducted in a similar style.
+
+```javascript
+let x = 5;
+x += 25; // x is now 30
+
+let y = 31;
+y %= 3; // y is now 1
+```
+
+[mdn-operator-precedence]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence#table