There are two boxes:
Box 1: 2 black + 4 red = 6 total balls
Box 2: 4 black + 3 red = 7 total balls
A ball is drawn at random from one of the two boxes. This means one box is randomly selected first, then a ball is drawn from that chosen box.
Probability of selecting Box 1 = 21
Probability of getting black from Box 1 = 62
Probability of selecting Box 1 and getting black = 21×62
=122
=61
Probability of selecting Box 2 = 21
Probability of getting black from Box 2 = 74
Probability of selecting Box 2 and getting black = 21×74
=144
=72
Total probability of getting a black ball = 61+72
LCM of 6 and 7 = 42
61=427
72=4212
Total probability = 427+4212
=4219
Therefore, the probability of getting a black ball is 4219.