This math topic focuses on calculating the percentage change when a number decreases by 10%. It is designed to help learners understand how to determine the percent decrease from an original number to a reduced number. Specifically, each problem presents an initial number and its 10% value, followed by a new smaller number, asking students to calculate the percent change resulting from the shrinkage. This topic forms part of a broader introduction to percentages, developing foundational skills in understanding and working with percent changes.