Need Help In Php - Topic

Member

Posts: 868

Joined: Jun 10 2010

Gold: 96.51

Feb 2 2013 09:07am

I need to calculate the chance that
rand(1,10)+rand(1,100) >=100
The answer is 6.5 and im really close with this script, something is wrong with it but i dont know what.

<?php
$alt=1;
$arg=1;
$current=0;
while($arg >= 10) {
$alt++;
if(($alt)+($arg) >= 100){
$current++;
}
if($alt = 100) {
$alt = 1;
$arg++;
}
}
echo $current;
echo ' '.$arg;
?>

I have also done

while($count < 10000) {
$arg = rand(1.0, 10.0);
$arg2 = rand(1.0,100.0);
$mart = $arg+$arg2;
if($mart >= 100) {
$count++;
}
else {
$nocount++;
}
}

echo $count.' '.$nocount;
$ugare = ($count/($count+$nocount))*100;
echo ' '.$ugare.' ';
echo ' '.substr($ugare, 0, 4);
?>

That works, by testing in cycles. But if i want an exact answer, wouldn't the top one be correct? If anyone could just point out the issue, because im sure its not anything major...
Thanks peace

Delson

Member

Posts: 14,109

Joined: Nov 6 2005

Gold: 1,939.00

Feb 3 2013 11:38am

Here you go. Result is 0.065 as you wished.

Code

<?php
//chance (rand(1,10)+rand(1,100) >=100)

//Idea: add all desired results and devide them by all possible results

$result=false;
$a=1; //first random number
$b=1; //second random number
$d=0; //number of desired results
$p=0; //number of all possibilities

while($a<=10){
$b=1;//set back $b to 1 after every loop
while($b<=100){
$c=$a+$b;
$result=check($c);
if($result){//check if the result was over 100
$d++;//add one desired result
}
$p++;
$b++;
}
$a++;
}

function check($random){
if($random>=100){
return true;
}
}

$chance=$d/$p;
echo $chance;

?>

Delson

Member

Posts: 14,109

Joined: Nov 6 2005

Gold: 1,939.00

Feb 3 2013 11:48am

Quote (Axelomahawk @ 2 Feb 2013 16:07)

To point out some of your mistakes:

Code

if($alt = 100) {

= means assignment and has nothing to do with comparison. You have to use == operator in this case

Then it is just about math. There is probably a formula you could use, I just decided to count all possibilities and make a simple division since the problem isn't that hard. It really seems you have to work on basics.

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