Previously, I tried using the automatic Pinterest RSS Feed but to no success. I even tried posting on the WordPress.com forum but again it did not address the problem. (To be fair, this is probably a problem on the Pinterest side.) Hence, the conclusion is that currently the WordPress.com to Pinterest automatic posting does not seem to work. (It apparently works for WordPress.org users according to my search on Google.)
Thus, I have manually added some pictures from Mathtuition88 (including reblogged content) onto Pinterest. Feel free to share it!
Manually adding pictures onto Pinterest is quite tedious and time-consuming. I will be monitoring how much effect Pinterest has, in terms of channelling traffic.