The main scale of vernier callipers reads in mm and its vernier scale is divided into 8 divisions which coincide with 5 divisions of the main scale. When the two jaws touch each other, the zero of the vernier coincides with the zero of main scale. When a rod is tightly placed along its length between the jaws, it is observed that the zero of vernier scale lies just left to `36^(th)` division of main scale and fourth division of vernier scale coincides with one main scale division. The measured value is (in cm)

Options

A. 3.66
B. 3.55
C. 3.65
D. 3.56

Answer

B

Explanation

M.S reading 35mm
`X + 4V = nM`
`X = nM - 4(5/8 M)`
`X lt 1` mm for `n = 3` only
So, `X=3-5/2=1/2mm`
`:.` reading = `35+0.5 mm`
` = 3.55 cm`.