VERNIER CALLIPER

The diameter of a spherical bob is measured using a vernier callipers . 9 divisions of the main scale ,in the vernier callipers ,are equal to 10 divisions of vernier scale .One main scale division is 1 mm . The main scale reading is 10mm and 8th division of vernier scale was found to coincide exactly with one of the main scale division .If the given vernier callipers has positive zero error of 0.04 cm , then the radius of the bob is __________ xx10^(-2) cm.

The length of a cylinder is measured with the help of a vernier callipers whose smallest division on the main scale is 0.5 mm and nine divisions of the main scale are equal to ten divisions of the vernier scale. It is observed that 78^("th") division of the main scale coincides with sixth division of the vernier callipers. Find the length of the cylinder.