What this lesson shows
A missing angle on a straight line: 180 − 65 = n.
The worked example
The lesson works this one step by step: 65° + n = 180°. Then your kid tries one like it on paper.
The steps
- A straight line is 180°
- Write it with n
- Subtract
- Add it back
Helping at home
A right angle is 90°, a straight line is 180°, and a full turn is 360°. Write the equation with n for the unknown angle, then subtract the known angle from the whole. Check by adding the two back, and by whether the angle looks smaller or wider than a right angle.
If your kid gets stuck
What do the two angles make together?
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.
Standards
- Common Core 4.MD.C.7
Recognize angle measure as additive. When an angle is decomposed into non-overlapping parts, the angle measure of the whole is the sum of the angle measures of the parts. Solve addition and subtraction problems to find unknown angles on a diagram in real world and mathematical problems, e.g., by using an equation with a symbol for the unknown angle measure.
Matches standards in 44 statesSee each state's code
- Alabama MA19.4.26a
- Alaska 4.MD.9
- Arizona 4.MD.C.7
- Arkansas 4.GM.3
- California 4.MD.C.7
- Colorado 4.MD.C.7
- Connecticut 4.MD.C.7
- Delaware 4.MD.C.7
- District of Columbia 4.MD.C.7
- Florida MA.4.GR.1.3
- Hawaii 4.MD.C.7
- Idaho 4.MD.C.7.a, 4.MD.C.7.b
- Illinois 4.MD.C.7
- Iowa 4.MD.C.7
- Kentucky KY.4.MD.7
- Louisiana 4.MD.C.7
- Maine 4.MD.C.7
- Maryland 4.GR.B.7
- Massachusetts 4.MD.C.7
- Michigan 4.MD.C.7
- Mississippi 4.MD.7
- Montana MT.4.MD.7, 4.D1.19
- Nebraska 4.G.2.e
- Nevada 4.MD.C.7
- New Hampshire 4.MD.C.7
- New Jersey 4.M.B.6
- New Mexico 4.MD.C.7
- New York NY-4.MD.7
- North Carolina NC.4.MD.6.c
- North Dakota 4.GM.M.7
- Ohio 4.MD.7
- Oregon 4.GM.C.9
- Pennsylvania CC.2.4.4.A.6
- Rhode Island 4.MD.C.7
- South Dakota 4.MD.C.7
- Tennessee 4.MD.C.7
- Texas 111.6.b.7.E
- Utah 4.MD.7.a, 4.MD.7.b
- Vermont 4.MD.C.7
- Virginia 5.MG.3h
- Washington 4.MD.C.7
- West Virginia M.4.25
- Wisconsin M.4.MD.C.7
- Wyoming 4.MD.7