Solving equation as fraction rather than decimal...Anyone?

[shamuraq]

Hi All,

 

I need to create this question in my worksheet. How many 1/3 are there in 3 wholes?

So i came out with these:

$ans = (1/3) / 3;

and i got

0.11111111111111

How do i solve this as a fraction?

[roopurt18]

First off your math is wrong.  There are 9 thirds in 3 wholes.

 

Computer math is always stored as integer or floating point.  You need to find a math library that supports fractions or write your own.

[shamuraq]

Yeah ur right. the equation part was wrong. My bad. But the math library. Any suggestion? To write my own would take years from now.

[roopurt18]

You might try this:

http://www.phpclasses.org/browse/package/4628.html

 

Following is a small bit of code I wrote to calculate probabilities.  A probability is just a fraction, i.e. 1 out of 6 or 1 / 6.  It may give you a couple hints of how you can construct your own if you can't find a pre-built solution:

 

<?php
class Probability {
    public $For = 0;
    public $Total = 0;
    
    /**
    * Returns NOT P
    * 
    * @param Probability $a
    * @return Probability
    */
    public static function NotP( Probability $a ) {
        return new Probability( $a->Total - $a->For, $a->Total );    
    }
    
    /**
    * Multiply two probabilities together
    * 
    * @return Probability
    */
    public static function Multiply() {
        $c = new Probability( 1, 1 );
        $args = func_get_args();
        foreach( $args as $arg ) {
            if( !($arg instanceof Probability) ) {
                throw new Exception( 'Argument is not a Probability instance ' . __METHOD__ );
            }
            $c->For *= $arg->For;
            $c->Total *= $arg->Total;
            $c->Reduce();
        }
        return $c->Reduce();
    }
    
    public function __construct( $for, $total ) {
        $this->For = (int)$for;
        $this->Total = (int)$total;  
        if( !$this->IsValid() ) { throw new Exception( 'Invalid probabiity: ' . $this ); }  
    }
    
    public function IsValid() {
        return $this->Total !== 0 && $this->For >= 0 && $this->For <= $this->Total;
    }
    
    public function Reduce() {
        $gcd = calc_gcd( $this->For, $this->Total );
        $this->For /= $gcd;
        $this->Total /= $gcd;
        return $this;    
    }
    
    public function __toString() {
        $against = $this->Total - $this->For;
        return "P: {$this->For} / {$this->Total}, !P: {$against} / {$this->Total}";
    }
    
    public function Value( $prec ) {
        $prec = (int)$prec;
        return round( 100 * $this->For / $this->Total, $prec );
    }
}

/**
* Reduce a fraction.
* 
* @param integer $num
* @param integer $den
*/
function frac_reduce( &$a, &$b ) {
    $gcd = calc_gcd( $a, $b );
    $a /= $gcd;
    $b /= $gcd;
}

/**
* Calculates the greatest common divisor of a bunch of numbers
* 
* @return integer
*/
function calc_gcd() {
    $args = func_get_args();
    foreach( $args as $k => $v ) {
        $v = (int)abs($v);
        if( $v === 0 ) {
            return 1;
        }
        $args[$k] = $v;
    }
    $min = call_user_func_array( 'min', $args );
    while( $min > 1 ) {
        $t = true;
        foreach( $args as $v ) {
            $t = $t && ($v % $min === 0);
            if( $t === false ) {
                break;
            }
        }
        if( $t === true ) {
            break;
        }
        $min--;
    }
    return $min;
}

?>

 

It's not the best code as I wrote it as a quick side project, but it may help. 

[shamuraq]

roopurt18, Thank you sooooo much mate... I'll give it a shot.