A vernier caliper (Non standard) is constructed which has one main scale division of length 1mm and 20 vernier scale divisions measure 18 mm. In an experiment, zero of vernier scale lies between 0.4 and 0.5 cm on main scale and 2^nd division of vernier scale coincides with a main scale division (when jaws of vernier are in closed position). When a cylinder whose diameter is to be measured is kept between the jaws of vernier caliper, the zero of vernier scale lies between 2.4 and 2.5 cm on main scale and 12^th division of vernier scale coincide with a main scale division. The diameter of cylinder in cm is