Multiply a given Integer with 3.5

2.3

Given a integer x, write a function that multiplies x with 3.5 and returns the integer result. You are not allowed to use %, /, *.

Examples:
Input: 2
Output: 7

Input: 5
Output: 17 (Ignore the digits after decimal point)

Solution:
1. We can get x*3.5 by adding 2*x, x and x/2. To calculate 2*x, left shift x by 1 and to calculate x/2, right shift x by 2.

C++

// C++ program to multiply
// a number with 3.5
#include <bits/stdc++.h>

int multiplyWith3Point5(int x)
{
    return (x<<1) + x + (x>>1);
} 

/* Driver program to test above functions*/
int main()
{
    int x = 4; 
    printf("%d", multiplyWith3Point5(x));
    getchar();
    return 0;
}

Java

// Java Program to multiply
// a number with 3.5

class GFG {
        
    static int multiplyWith3Point5(int x)
    {
        return (x<<1) + x + (x>>1);
    } 
    
    /* Driver program to test above functions*/
    public static void main(String[] args)
    {
        int x = 2; 
        System.out.println(multiplyWith3Point5(x));
    }
}

// This code is contributed by prerna saini.



2. Another way of doing this could be (8*x – x)/2 (See below code). Thanks to ajaym for suggesting this.

#include <stdio.h>
int multiplyWith3Point5(int x)
{
  return ((x<<3) - x)>>1;
}    

Please write comments if you find the above code/algorithm incorrect, or find better ways to solve the same problem

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2.3 Average Difficulty : 2.3/5.0
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