Adding and Subtracting Angles
Aligned to 4.MD.C.7 — Common Core State Standards for Mathematics.
What this lesson teaches
When a big angle is split into smaller angles that do not overlap, the small angle measures add up to the big one. If you know the whole and one part, subtract to find the missing part.
Worked example
A 80 degree angle is split into two parts. One part is 30 degrees. What is the other part? The two parts add to 80, so subtract the known part: 80 - 30 = 50. The missing angle is 50 degrees. Check: 30 + 50 = 80.
Practice questions
- Two angles of 25 and 40 degrees sit side by side. What is the total angle?
- A 90 degree angle is split into 55 degrees and one unknown angle. Find the unknown.
- An angle of 120 degrees is divided into three equal parts. How big is each part?
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
Sumar y restar angulos
Cuando un angulo grande se divide en angulos mas pequenos que no se traslapan, las medidas de los angulos pequenos se suman para dar el grande. Si conoces el total y una parte, resta para hallar la parte que falta.
Ejemplo: Un angulo de 80 grados se divide en dos partes. Una parte es de 30 grados. Cuanto mide la otra parte? Las dos partes suman 80, asi que resta la parte conocida: 80 - 30 = 50. El angulo que falta mide 50 grados. Comprueba: 30 + 50 = 80.
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