Since the picture was enlarged by a factor of 100, divide 29 centimeters (the length in the photo) by 100 (the factor of enlargement) to get the actual length.
29/100 = 0.29 centimeters
Thus, the actual length of the deer tick is 0.29 centimeters.
If you need the length in millimeters, multiply 0.29 with 10, and you get 2.9 millimeters.
