A formal operations problem was administered to 64 first-, third-, fifth-, and seventh-grade children to examine problem solving strategy as a function of age and of exposure to an audio-tape cassette of a child model who exhibited the optimal strategy for problem solution. Results were analyzed in terms of strategy where the best strategy was a constraint-seeking one in which each question reduced uncertainty by one-half. Performance improved with age (p < .01); the main effect for the modeling condition was also significant (p < .05). Results were discussed in Piagetian terms and in learning by modeling after the work of Bandura.