A boy uses a vernier callipers to measure the thickness of his pencil. He measures it to be 1.4mm. If the zero error of vernier callipers is +0.02cm, what is the correct thickness of pencil?

As we know,

Correct reading = observed reading – zero error (with sign)

Given,

The thickness of the pencil = 1.4 mm

Zero error of the vernier callipers = +0.02cm = 0.2 mm

Substituting the values in the formula above we get,

Correct reading = observed reading – zero error (with sign)

Correct reading = 1.4 mm – 0.2 mm

Correct reading = 1.2 mm

Hence, the correct thickness of the pencil is 1.2 mm