# Multiply a number by 15 without using * and / operators

Given a integer N, the task is to multiply the number with 15 without using multiplication * and division / operators.

Examples:

Input: N = 10
Output: 150

Input: N = 7
Output: 105

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Method 1: We can multiply integer N by 15 using bitwise operators. First left shift the number by 4 bits which is equal to (16 * N) then subtract the original number N from the shifted number i.e. ((16 * N) – N) which is equal to 15 * N.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach ` `#include ` `using` `namespace` `std; ` ` `  `// Function to return (15 * N) without ` `// using '*' or '/' operator ` `long` `multiplyByFifteen(``long` `n) ` `{ ` `    ``// prod = 16 * n ` `    ``long` `prod = (n << 4); ` ` `  `    ``// ((16 * n) - n) = 15 * n ` `    ``prod = prod - n; ` ` `  `    ``return` `prod; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``long` `n = 7; ` ` `  `    ``cout << multiplyByFifteen(n); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java implementation of the approach ` `class` `GFG { ` ` `  `    ``// Function to return (15 * N) without ` `    ``// using '*' or '/' operator ` `    ``static` `long` `multiplyByFifteen(``long` `n) ` `    ``{ ` `        ``// prod = 16 * n ` `        ``long` `prod = (n << ``4``); ` ` `  `        ``// ((16 * n) - n) = 15 * n ` `        ``prod = prod - n; ` ` `  `        ``return` `prod; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``long` `n = ``7``; ` `        ``System.out.print(multiplyByFifteen(n)); ` `    ``} ` `} `

## Python

 `# Python3 implementation of the approach  ` ` `  `# Function to return (15 * N) without  ` `# using '*' or '/' operator ` `def` `multiplyByFifteen(n): ` `     `  `    ``# prod = 16 * n ` `    ``prod ``=` `(n << ``4``) ` `     `  `    ``# ((16 * n) - n) = 15 * n ` `    ``prod ``=` `prod ``-` `n ` `     `  `    ``return` `prod ` `     `  `# Driver code ` `n ``=` `7` `print``(multiplyByFifteen(n)) `

## C#

 `// C# implementation of the approach ` `using` `System; ` `class` `GFG { ` ` `  `    ``// Function to return (15 * N) without ` `    ``// using '*' or '/' operator ` `    ``static` `long` `multiplyByFifteen(``long` `n) ` `    ``{ ` `        ``// prod = 16 * n ` `        ``long` `prod = (n << 4); ` ` `  `        ``// ((16 * n) - n) = 15 * n ` `        ``prod = prod - n; ` ` `  `        ``return` `prod; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``long` `n = 7; ` `        ``Console.Write(multiplyByFifteen(n)); ` `    ``} ` `} `

## PHP

 ` `

Output:

```105
```

Method 2: We can also calculate the multiplication (15 * N) as sum of (8 * N) + (4 * N) + (2 * N) + N which can be obtained by performing left shift operations as (8 * N) = (N << 3), (4 * N) = (n << 2) and (2 * N) = (n << 1).

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach ` `#include ` `using` `namespace` `std; ` ` `  `// Function to return (15 * N) without ` `// using '*' or '/' operator ` `long` `multiplyByFifteen(``long` `n) ` `{ ` `    ``// prod = 8 * n ` `    ``long` `prod = (n << 3); ` ` `  `    ``// Add (4 * n) ` `    ``prod += (n << 2); ` ` `  `    ``// Add (2 * n) ` `    ``prod += (n << 1); ` ` `  `    ``// Add n ` `    ``prod += n; ` ` `  `    ``// (8 * n) + (4 * n) + (2 * n) + n = (15 * n) ` `    ``return` `prod; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``long` `n = 7; ` ` `  `    ``cout << multiplyByFifteen(n); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java implementation of the approach ` `class` `GFG { ` ` `  `    ``// Function to return (15 * N) without ` `    ``// using '*' or '/' operator ` `    ``static` `long` `multiplyByFifteen(``long` `n) ` `    ``{ ` `        ``// prod = 8 * n ` `        ``long` `prod = (n << ``3``); ` ` `  `        ``// Add (4 * n) ` `        ``prod += (n << ``2``); ` ` `  `        ``// Add (2 * n) ` `        ``prod += (n << ``1``); ` ` `  `        ``// Add n ` `        ``prod += n; ` ` `  `        ``// (8 * n) + (4 * n) + (2 * n) + n = (15 * n) ` `        ``return` `prod; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``long` `n = ``7``; ` `        ``System.out.print(multiplyByFifteen(n)); ` `    ``} ` `} `

## Python

 `# Python3 implementation of the approach  ` ` `  `# Function to perform Multiplication ` `def` `multiplyByFifteen(n): ` `     `  `    ``# prod = 8 * n ` `    ``prod ``=` `(n << ``3``) ` `     `  `    ``# Add (4 * n) ` `    ``prod ``+``=` `(n << ``2``) ` `     `  `    ``# Add (2 * n) ` `    ``prod ``+``=` `(n << ``1``) ` `     `  `    ``# Add n ` `    ``prod ``+``=` `n ` `     `  `    ``# (8 * n) + (4 * n) + (2 * n) + n = (15 * n) ` `    ``return` `prod ` `     `  `# Driver code ` `n ``=` `7` `print``(multiplyByFifteen(n)) `

## C#

 `// C# implementation of the approach ` `using` `System; ` `class` `GFG { ` ` `  `    ``// Function to return (15 * N) without ` `    ``// using '*' or '/' operator ` `    ``static` `long` `multiplyByFifteen(``long` `n) ` `    ``{ ` `        ``// prod = 8 * n ` `        ``long` `prod = (n << 3); ` ` `  `        ``// Add (4 * n) ` `        ``prod += (n << 2); ` ` `  `        ``// Add (2 * n) ` `        ``prod += (n << 1); ` ` `  `        ``// Add n ` `        ``prod += n; ` ` `  `        ``// (8 * n) + (4 * n) + (2 * n) + n = (15 * n) ` `        ``return` `prod; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``long` `n = 7; ` `        ``Console.Write(multiplyByFifteen(n)); ` `    ``} ` `} `

Output:

```105
```

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