# In a vernier calliper if the vernier is on the right side of the zero of the main scale and nth vernier scale division coincides with main scale division correct reading is

$(a)\;\text{observation reading - n$\times$least count} \\(b)\;\text {observation reading + n$\times$least count} \\(c)\;\text{observation reading$\times$least count} \\(d)\;\text{none}$

When zero of vernier is to the right of the zero of main scale the error is positive and is to be subtracted from the observed reading .
Zero error $=+n \times$ Least count
$\qquad$=Observed reading $- n \times$ least count
Hence a is the correct answer.
edited Apr 3, 2014 by meena.p