Posted by aswath on .
A round bar 40mm diameter is subjected to an axial pull of 80kN and
reduction in diameter was found to be 0.00775mm. Find Poisson's ratio and
Young's modules for the material of the bar. Take value of shear modules as
40kN/mm0…5.

math 
drwls,
You want to know Young's and the shear modulus, E and G, not Young's and shear modules.
The equations you need can be found at
http://silver.neep.wisc.edu/~lakes/PoissonIntro.html
Your last sentence is incomplete.