diff --git a/Project Euler/Problem1.js b/Project Euler/Problem1.js
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+/*    Multiples of 3 and 5
+    If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
+Find the sum of all the multiples of 3 or 5 below the provided parameter value number.
+*/
+
+function multiplesThreeAndFive (num) {
+  let total = 0
+  // total for calculating the sum
+  for (let i = 0; i <= num; i++) {
+    if (i % 3 === 0 || i % 5 === 0) {
+      total += i
+    }
+  }
+  return total
+}
+
+var num = console.log('Enter a number: ')
+console.log(multiplesThreeAndFive(num)) // multiples3_5 function to calculate the sum of multiples of 3 and 5 within num