Rats grow to their environment.. they can be little or huge.. and it's depending if it's male or female..
Rats can range from 1-2'' ('pinky rats') to 8-9'' long. It really is a huge range. You can check this website, which sells rats frozen to people who have snakes for pets. It describes the length and weight of different sized rats available for purchase. You can ask your teacher if the rats have been tiny, small, medium or large in the past, and then look at the chart and get an idea.
http://www.ratsicles.com/frozen_feeder_rats.htmlHow many hairs does the average dog have?
I would tell you the length of body and tail and total length but it's pointless so I will use body parts :P they can get the side of your wrist to your hand and sometimes your wrist to your hand plus a pinky (last finger) taller. their width depends on how you feed. Ideally their width is the length of your middle finger. They can get bigger though :P.How many puppies come in a Chihuahua litter?