$ cat pogo.pl
#!/usr/bin/perl
use strict;
use warnings;
use Number::Fraction;

my %tasks = (
    a=>4, b=>4, c=>4, d=>24, e=>24, f=>24, g=>100, h=>150, i=>150, j=>150, k=>600
);

my $time = 0;
for my $k (sort keys %tasks) {
    my $time_used = Number::Fraction->new( 1, $tasks{$k});
    $time = $time + $time_used;
    print $time->to_string(), "\n";
}
$ ./pogo.pl
1/4
1/2
3/4
19/24
5/6
7/8
177/200
107/120
539/600
181/200
68/75