Two studies were used to examine developmental and task effects in estimation problems. Time to solution data were collected on students' performance to describe their efficiency in processing information. Study One demonstrated developmental differences in speed of processing between younger students (first grade) and older students (third and sixth grade), with younger students performing at a slower rate. Study Two demonstrated that the amount of feedback information present influenced speed of processing. Results were discussed in terms of student and task characteristics and the implications of such variables for an information processing model of learning. Implications for science teaching were also discussed in terms of diagnosing learning problems and designing science curriculum.