Triangles two ways: 5th grade math lesson

What this lesson shows

By sides: equilateral, isosceles, scalene. By angles: acute, right, obtuse. Each triangle gets one of each.

The worked example

The lesson works this one step by step: an equilateral acute triangle, an isosceles right triangle, a scalene obtuse triangle. Then your kid tries one like it on paper.

The steps

Sides: equilateral, isosceles, scalene
Angles: acute, right, obtuse
One name of each

Helping at home

Name every triangle twice. By sides: 3 equal is equilateral, exactly 2 equal is isosceles, none equal is scalene. By angles: one right angle is right, one obtuse angle is obtuse, all three acute is acute. Mark equal sides with matching ticks.

If your kid gets stuck

One name from the sides, one from the angles.

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.

See how Lux works

Standards

Common Core 5.G.B.4
Classify two-dimensional figures in a hierarchy based on properties.

Matches standards in 50 statesSee each state's code

Alabama MA19.5.21, MA19.5.22
Alaska 5.G.4
Arizona 5.G.B.4
Arkansas 5.GM.1
California 5.G.B.4
Colorado 5.G.B.4
Connecticut 5.G.B.4
Delaware 5.G.B.4
District of Columbia 5.G.B.4
Florida MA.5.GR.1.1
Georgia 5.GSR.8.1
Hawaii 5.G.B.4
Idaho 5.G.B.4
Illinois 5.G.B.4
Indiana 5.G.1, 4.G.3
Iowa 5.G.B.4
Kansas 4.G.2, 5.G.4
Kentucky KY.5.G.4
Louisiana 5.G.B.4
Maine 5.G.B.4
Maryland 5.GR.B.3.a, 5.GR.B.3.b
Massachusetts 5.G.B.4
Michigan 5.G.B.4
Minnesota 4.3.1.1
Mississippi 4.G.2, 5.G.3, 5.G.4
Missouri 5.GM.A.2
Montana MT.5.G.4, 5.D1.4, 5.D1.18, 5.D2.2
Nebraska 5.G.1.c
Nevada 5.G.B.4
New Hampshire 5.G.B.4
New Jersey 5.G.B.4
New Mexico 5.G.B.4
New York NY-4.G.2.a, NY-5.G.3, NY-5.G.4
North Carolina NC.4.G.2, NC.5.G.3.b
North Dakota 5.GM.G.1
Ohio 5.G.3, 5.G.4
Oklahoma 4.GM.1.2, 5.GM.1.1
Oregon 5.GM.B.3
Pennsylvania CC.2.3.5.A.2
Rhode Island 5.G.B.4
South Carolina 4.MGSR.3.1, 4.MGSR.3.2
South Dakota 4.G.A.2, 5.G.B.4
Tennessee 5.G.B.3
Texas 111.6.b.6.C, 111.7.b.5
Utah 5.G.4
Vermont 5.G.B.4
Virginia 4.MG.5a, 4.MG.5c, 4.MG.5d.i, 4.MG.5d.ii, 4.MG.5d.iii, 4.MG.5d.iv, 5.MG.3b, 5.MG.3c, 5.MG.3d
Washington 5.G.B.4
West Virginia M.5.26
Wisconsin M.5.G.B.4

Triangles two ways