# Given a number n, count all multiples of 3 and/or 5 in set {1, 2, 3, … n}

• Last Updated : 03 Nov, 2021

Given a number n, count all multiples of 3 and/or 5 in set of numbers from 1 to n.
Examples:

```Input: n = 6
Output: 3
There are three multiples of 3 and/or 5 in {1, 2, 3, 4, 5, 6}

Input: n = 16
Output: 7
There are two multiples of 7 and/or 5 in {1, 2, .. 16}
The multiples are 3, 5, 6, 9, 10, 12, 15```

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The value of n/3 gives us number of multiples of 3, the value of n/5 gives us number of multiples of 5. But the important point is there are may be some common multiples which are multiples of both 3 and 5. We can get such multiples by using n/15. Following is the program to find count of multiples.

## C++

 `// C++ program to find count of multiples of 3 and 5 in {1, 2, 3, ..n}``#include ``using` `namespace` `std;` `unsigned countOfMultiples(unsigned n)``{``   ``// Add multiples of 3 and 5.  Since common multiples are``   ``// counted twice in n/3 + n/15, subtract common multiples``   ``return` `(n/3 + n/5 - n/15);``}` `// Driver program to test above function``int` `main()``{``   ``cout << countOfMultiples(6) << endl;``   ``cout << countOfMultiples(16) << endl;``   ``return` `0;``}`

## Java

 `// Java program to find count of multiples``// of 3 and 5 in {1, 2, 3, ..n}``import` `java .io.*;``class` `GFG {``    ` `    ``static` `long` `countOfMultiples(``long` `n)``    ``{``        ` `        ``// Add multiples of 3 and 5.``        ``// Since common multiples are``        ``// counted twice in n/3 + n/15,``        ``// subtract common multiples``        ``return` `(n/``3` `+ n/``5` `- n/``15``);``    ``}``    ` `    ``// Driver Code``    ``static` `public` `void` `main (String[] args)``    ``{``        ``System.out.println(countOfMultiples(``6``));``        ``System.out.println(countOfMultiples(``16``));``    ``}``}` `// This code is contributed by anuj_67.`

## Python3

 `# python program to find count``# of multiples of 3 and 5 in``# {1, 2, 3, ..n}` `def` `countOfMultiples(n):``    ``# Add multiples of 3 and 5.``    ``# Since common multiples are``    ``# counted twice in n/3 + n/15,``    ``# subtract common multiples``    ``return` `(``int``(n``/``3``) ``+` `int``(n``/``5``) ``-` `int``(n``/``15``));`  `# Driver program to test``# above function``print``(countOfMultiples(``6``))``print``(countOfMultiples(``16``))` `# This code is contributed by Sam007.`

## C#

 `// C# program to find count of multiples``// of 3 and 5 in {1, 2, 3, ..n}``using` `System;` `public` `class` `GFG {``    ` `    ``static` `uint` `countOfMultiples(``uint` `n)``    ``{``        ``// Add multiples of 3 and 5.``        ``// Since common multiples are``        ``// counted twice in n/3 + n/15,``        ``// subtract common multiples``        ``return` `(n/3 + n/5 - n/15);``    ``}``    ` `    ``// Driver program to test above``    ``// function``    ``static` `public` `void` `Main ()``    ``{``        ``Console.WriteLine(countOfMultiples(6));``        ` `        ``Console.WriteLine(countOfMultiples(16)) ;``    ``}``}` `// This code is contributed by anuj_67.`

## PHP

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## Javascript

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Output:

```3
7```

Time Complexity: O(1)

Auxiliary Space: O(1)