Using Similarity and Congruence
Aligned to G-SRT.B.5 — Common Core State Standards for Mathematics.
What this lesson teaches
Similar figures have the same shape with proportional sides; congruent figures are identical. Use these relationships to find unknown lengths.
Worked example
Two similar triangles: small has sides 3,4,5; large has matching side 6 (twice 3), so its other sides are 8 and 10.
Practice questions
- Triangles are similar with scale factor 3. A side of 5 becomes what?
- How are congruent and similar different?
- Find a missing side using a proportion of two similar shapes.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Uso de semejanza y congruencia
Las figuras semejantes tienen la misma forma con lados proporcionales; las figuras congruentes son idénticas. Usa estas relaciones para encontrar medidas desconocidas.
Ejemplo: Dos triángulos semejantes: el pequeño tiene lados 3, 4, 5; el grande tiene el lado correspondiente 6 (el doble de 3), por lo que sus otros lados son 8 y 10.
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