Illuminations: Sliding Triangle

Illuminations: Sliding Triangle

Sliding Triangle

The triangle above lies on a flat surface and is pushed at the top vertex. The length of the congruent sides does not change, but the angle between the two congruent sides will increase, and the base will stretch. Initially, the area of the triangle will increase, but eventually the area will decrease, continuing until the triangle collapses.

What is the maximum area achieved during this process? And, what is the length of the base when this process is used to create a different triangle whose area is the same as the triangle above?

This brainteaser was written by Derrick Niederman.


National Council of Teachers of Mathematics
Math Topics
Area, Perimeter & Volume, Geometry
K-6, Middle School, High School
6th Grade, 7th Grade, 8th Grade, 9th Grade, 10th Grade
Descriptions of PDFs

Problem and Solution

What are you looking for?

Organization

National Council of Teachers of Mathematics

Website URL

Type of Resource

Activity Sheet
PDF File

Assigned Categories

Resource k12

Illuminations: Sliding Triangle

Sliding Triangle

The triangle above lies on a flat surface and is pushed at the top vertex. The length of the congruent sides does not change, but the angle between the two congruent sides will increase, and the base will stretch. Initially, the area of the triangle will increase, but eventually the area will decrease, continuing until the triangle collapses.

What is the maximum area achieved during this process? And, what is the length of the base when this process is used to create a different triangle whose area is the same as the triangle above?

This brainteaser was written by Derrick Niederman.

National Council of Teachers of Mathematics
Math Topics
Area, Perimeter & Volume, Geometry
K-6, Middle School, High School
6th Grade, 7th Grade, 8th Grade, 9th Grade, 10th Grade
Descriptions of PDFs

Problem and Solution

What are you looking for?

Organization

National Council of Teachers of Mathematics

Website URL

Type of Resource

Activity Sheet
PDF File

Assigned Categories