Final answer:
Without statistical data, such as a correlation coefficient between high jump and long jump performances, it is not possible to determine the percentage of variability in long jumps accounted for by high-jump performances.
Step-by-step explanation:
The question asked by the student pertains to the relationship between two athletic events: the long jump and the high jump, and specifically, how the performance in one might predict the performance in the other. However, without a provided correlation coefficient or additional statistical data, it is not possible to accurately answer what percentage of the variability in long jumps can be accounted for by high-jump performances. In statistics, this type of relationship is often quantified using a correlation coefficient, which is squared to get the coefficient of determination (R-squared value). The R-squared value represents the proportion of the variance for the dependent variable that's explained by an independent variable in a regression model. But since we do not have any specific values or data in the question, we must assume that this is a theoretical or incomplete question and we cannot provide a specific answer.