This document contains a retrospective sheet from Gokul Academy of Science dated January 10-13, 2012. It includes the following: 1) Questions from January 10th about solving simultaneous equations and defining frequency and how many times a sound source of 100Hz vibrates in a minute. 2) Questions from January 11th about solving systems of equations and defining reverberation and how it can be reduced. 3) Questions from January 12th about solving systems of linear equations, defining longitudinal/transverse waves, and the audible range of sound. 4) Questions from January 13th about finding values of expressions without solving variables explicitly, and defining sound, echo, and the long form of S