The internal and external diameters of a hollow cylinder are measured with the help of a Vernier Callipers. Their values are 4.23 \(\pm\) 0.01 cm and 3.87 \(\pm\) 0.01 cm, respectively. The thickness of the wall of the cylinders is : 

0.18 \(\pm\) 0.02 cm

Thickness : t = \(\frac{4.23-3.87}{2}\)

t = 0.18 cm

Error = \(\Delta r_1\) + \(\Delta r_2\)

        = \(\pm\) (0.01 + 0.01) cm

        = \(\pm\) 0.02 cm

Thickness : t = (0.18 \(\pm\) 0.02) cm