Given a number n, the task is to find the sum of the geometric series in PHP. A Geometric series is a series with a constant ratio between successive terms. The first term of the series is denoted by a and the common ratio is denoted by r.
PHP Program to Sum of Geometric Series using for Loop
A Simple solution to calculate the sum of geometric series. Here, we use a for loop to find the sum of the Geometric Series.
Example: PHP Program to find the sum of geometric series using a for loop.
<?php function geometricSum( $a , $r , $n ) {
$sum = 0;
for ( $i = 0; $i < $n ; $i ++){
$sum = $sum + $a ;
$a = $a * $r ;
}
return $sum ;
} // Driver code $a = 2; // First term
$r = 3; // Common ratio
$n = 4; // Number of terms
echo "Sum of Geometric Series: " . geometricSum( $a , $r , $n );
?> |
Sum of Geometric Series: 80
PHP Program to Sum of Geometric Series using Mathematical Formula
The series looks like this :- a, ar, ar2, ar3, ar4, . . .
Sum of series Sn = a×(1−rn)1−rSn=1−ra×(1−rn)
Where:
- Sn: The sum of the geometric series up to the nth term.
- a: The first term of the series.
- r: The common ratio of the series.
- n: The number of terms in the series.
Example: PHP Program to find the sum of geometric series using a mathematical formula.
<?php function geometricSum( $a , $r , $n ) {
if ( $r == 1) {
return $a * $n ;
}
// Calculate the sum of geometric series
$sum = $a * (1 - pow( $r , $n )) / (1 - $r );
return $sum ;
} // Driver code $a = 2; // First term
$r = 3; // Common ratio
$n = 4; // Number of terms
echo "Sum of Geometric Series: " . geometricSum( $a , $r , $n );
?> |
Sum of Geometric Series: 80