Answer Happy

I just need help about poisson ratio? show me how to answer the question and I can learn how to figure out other variations.
Question 1: Determine the shear modulus for a magnesium alloy that has a modulus E=6.5∗106 psi and Poisson's ratio v=0.340. Question 2: Determine Poisson's ratio for a cast iron that has a modulus of E=12∗106psi and a shear modulus G=4.8∗106psi. Question 3: A solid circular shaft has a diameter of 50 mm. If the torque applied is 2.25kN.m, what is the maximum shearing stress? Question 4: A hollow aluminum shaft has an outside diameter of 2.50 in. and an inside diameter of 2.25 in. What is the maximum shearing stress if a torque of 21,500lb-in. is applied? Question 5: A circular aluminum alloy tube has an outside diameter of 4 in. and an inside diameter of 3.4 in. What is the angle of twist in degrees if the torque applied is 30,000lb-in. and the shaft is 4.5ft long? GAl​=12∗106psi