From ed01146224b6801a85e5bdc9daa568d0f1b7cf58 Mon Sep 17 00:00:00 2001
From: Inuka Wijerathna <inukawijerathna210@gmail.com>
Date: Fri, 5 Jun 2026 10:43:53 +0530
Subject: [PATCH] Add ReturnOnInvestment to Maths

---
 Maths/ReturnOnInvestment.php | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 Maths/ReturnOnInvestment.php

diff --git a/Maths/ReturnOnInvestment.php b/Maths/ReturnOnInvestment.php
new file mode 100644
index 0000000..7c0b020
--- /dev/null
+++ b/Maths/ReturnOnInvestment.php
@@ -0,0 +1,22 @@
+<?php
+
+/**
+ * Calculates Return on Investment (ROI) as a percentage.
+ * ROI measures the profitability of an investment relative to its cost.
+ *
+ * Formula: ROI = (Gain - Cost) / Cost * 100
+ *
+ * @see https://www.investopedia.com/terms/r/returnoninvestment.asp
+ *
+ * @param float $gainFromInvestment total value gained from the investment
+ * @param float $costOfInvestment   total cost of the investment
+ * @return float ROI as a percentage
+ * @throws \InvalidArgumentException if costOfInvestment is not positive
+ */
+function returnOnInvestment(float $gainFromInvestment, float $costOfInvestment): float
+{
+    if ($costOfInvestment <= 0) {
+        throw new \InvalidArgumentException('costOfInvestment must be greater than 0');
+    }
+    return ($gainFromInvestment - $costOfInvestment) / $costOfInvestment * 100;
+}