1. The problem statement, all variables and given/known data Let S and S' be two inertial frames of reference where S' is moving at a velocity of 0.6c relative to S. When x = x' = 0, t = t' = 0, where t and t' are time of the clocks on S and S' respectively and x and x' are the x-coordinates of the S and S' frames respectively. An event occurs at S when t = 2 × 10-7s and x = 50m. What is t' when the event occurs at S'? 2. Relevant equations t = ϒ t' 3. The attempt at a solution Let t' be the proper time. t = ϒ t' where t = 2 × 10-7s and v = 0.6c. Solving, I got t' = 1.6 × 10-7s but the answer is 1.25 × 10-7s. What am I doing wrong?