$5 RED balls +5 BLACK balls = Total 10 balls Here we have two cases. Case -1: First ball drawn is RED and second ball drawn is also RED Case-2: First ball drawn is BLACK and second ball drawn is RED Probability of FIRST drawn ball is RED and SECOND drawn ball is RED = 5/10 * 4/9 = 20/90 Probability of FIRST drawn ball is BLACK and SECOND ball is RED =5/10* 5/9= 25/90 Required probability = 20/90 + 25/90 = 1/2