A manufacturer makes 3 models of a TV, models A, B and C. A store sells 40% model A sets, 40% model B sets and 20% model C sets. Of model A sets, 3% have stereo sound; of model B sets, 7% have stereo sound, and of model C sets, 9% have stereo sound. If a set is sold at random, find the probability that it has stereo sound.
Attempt:
Total Stereo sets: 3% of 40 + 7% of 40 + 9% of 20 = 5.8%
Therefore, would the probability of a set being chosen at random having stereo sound be 5.8%?
I like to think in terms of pictures...