Regarding progressbar update

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C#

I'm using a similar code:

private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            progressBar1.Value = e.ProgressPercentage;
        }

        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            MessageBox.Show("Complete");
        }


        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {

            int[] arr = new int[21];
            for (int i = 1; i <= 20; i++)
            {
                arr[i] = i;
                Thread.Sleep(100);
                int m = (i/arr.Length)*100;
                backgroundWorker1.ReportProgress(i*m);
            }
        }

The progress bar isn't updating. But if I replace m by 5 the progress is seen. Please help.. In the original program I have to use the above approach. Thanks. :)