Least count = 0.01cm
Main scale reading (MSR) = 2.4cm
Vernier scale divisions (VSD) = 6.
The instruments have a negative error.
e = (-5 × 0.01)
e = -0.05cm
So the total reading of the diameter of the sphere
R = MSR+(VSD×LC)+ zero error
R = 2.4 + (6 × 0.01) + (0.05)
R = 2.51cm