Grades 11-12 Video Solutions 2010-11&12 Video Solutions 2010 problem21

11&12 Video Solutions 2010 problem21

Video Transcription

Video Summary

The problem involves a rectangular piece of paper being folded three times, requiring the measurement of angle beta given angle alpha as 70 degrees. By analyzing the folding process, the 180-degree angle sum rule is applied to calculate intermediate angles, determining a vital angle gamma (40 degrees). Using the properties of folded shapes, particularly a parallelogram formed by the fold, and considering symmetry and angle sums, the solution found that angle beta equates to 120 degrees. Therefore, the correct answer is 120 degrees.

Keywords

paper folding

angle calculation

geometry

parallelogram

symmetry