Question

How to find the sum of all the multiples of 3 or 5 below 10 in PHP

Answer 1

$sum = 0;

for ($i = 3; $i < 10; $i++) {
    if ($i % 3 == 0 || $i % 5 == 0) {
        echo $i . "\n";
        $sum += $i;
    }
}

echo "sum = " . $sum;




/*
run:

3
5
6
9
sum = 23

*/

 

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Answer 2

function Sum($n) {
    return (int)(($n * ($n + 1)) / 2);
}
         
$below10 = 9;
$sum = 3 * Sum((int)($below10 / 3)) + 5 * Sum((int)($below10 / 5)) - (3 * 5) * Sum((int)($below10 / 15));
 
echo "sum = " . $sum;
 
 
 
 
/*
run:
 
sum = 23
 
*/

 

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