There are two methods for **calculating sum of first n say 20 even numbers**

**First method** – using For Loop :

#### You can calculate some of first n numbers using for loop, see the code below :

```
<?php
$n = 20;
$currEven = 2;
$sumEven = 0;
//using for loop for calculating sum of first n even numbers
for ($i = 1; $i <= $n; $i++) {
$sumEven += $currEven;
// next even number
$currEven += 2;
}
echo "Sum of first $n even numbers is : ".$sumEven ;
?>
```

** Second method** – using formula :

#### You can calculate some of first n numbers using formula, see the code below :

```
<?php
$n = 20;
// using formula for calculating sum of first n even numbers
$sum= ($n * ($n + 1));
echo "Sum of first $n even numbers is : $sum" ;
?>
```

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