What this lesson shows
Tear off a triangle's three corners and line them up: a straight line, 180 degrees. With 50° and 70° known, the third angle is 60°.
The worked example
The lesson works this one step by step: 50° + 70° + n = 180°. Then your kid tries one like it on paper.
The steps
- Three angles make 180°
- Add the two you know
- Subtract from 180
- Add all three
Helping at home
The three angles of any triangle add to 180°: torn off and put point to point, they make a straight line. Add the two you know, subtract from 180, and check by adding all three.
If your kid gets stuck
What do all three angles add to?
Watch it with Lux
With Lux, this lesson is a narrated video and a printed page your kid works on. Then Lux helps with the same math on their own worksheet, one question at a time.
More in this unit
- Triangles two ways
- Every name that fits
- Not only the last name
- Solid figures
- Turning does not change it
- Volume by packing cubes
- No gaps, no overlaps
- Volume by formula
- The base is an area
- Find the missing edge
- Two boxes put together
- Nets of solids
- Area of parallelograms and triangles
- Area of a trapezoid
- Estimating around a curve
- Radius and diameter
- Perimeter, area, or volume?
- Surface area with a net