Adding tops and bottoms: 5th grade math lesson

What this lesson shows

Fixes a mistake

1/2 + 1/3 is not 2/5. Halves and thirds are different units, so rename first.

The worked example

The lesson works this one step by step: 1/2 + 1/3. Then your kid tries one like it on paper.

The steps

Adding bottoms makes it too small
Rename in the same parts
Add only the tops

Helping at home

Never add the bottoms. Different bottoms mean different sizes of parts, so rename both in the same parts first, then add only the tops. A sum must be bigger than each fraction in it: check the answer that way.

If your kid gets stuck

Rename first. Add only the tops.

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.NF.A.1
Add and subtract fractions with unlike denominators (including mixed numbers) by replacing given fractions with equivalent fractions in such a way as to produce an equivalent sum or difference of fractions with like denominators. For example, 2/3 + 5/4 = 8/12 + 15/12 = 23/12. (In general, a/b + c/d = (ad + bc)/bd.)

Matches standards in 49 statesSee each state's code

Alabama MA19.5.10
Alaska 5.NF.1
Arizona 5.NF.A.1
Arkansas 5.CAR.5
California 5.NF.A.1
Colorado 5.NF.A.1
Connecticut 5.NF.A.1
Delaware 5.NF.A.1
District of Columbia 5.NF.A.1
Florida MA.5.FR.2.1
Georgia 5.NR.3.3
Hawaii 5.NF.A.1
Idaho 5.NF.A.1
Illinois 5.NF.A.1
Indiana 5.CA.3
Iowa 5.NF.A.1
Kansas 5.NF.1
Kentucky KY.5.NF.1
Louisiana 5.NF.A.1
Maine 5.NF.A.1
Maryland 5.NOS.C.8.b, 5.NOS.C.8.c
Massachusetts 5.NF.A.1
Michigan 5.NF.A.1
Minnesota 5.1.3.1, 5.1.3.2
Mississippi 5.NF.1
Missouri 5.NF.B.6
Montana MT.5.NF.1, 5.D2.5, 5.D3.4
Nebraska 5.N.3.e
Nevada 5.NF.A.1
New Hampshire 5.NF.A.1
New Jersey 5.NF.A.1
New Mexico 5.NF.A.1
New York NY-5.NF.1
North Dakota 5.NO.NF.3
Ohio 5.NF.1
Oklahoma 5.N.3.3
Oregon 5.NF.A.1
Pennsylvania CC.2.1.5.C.1
Rhode Island 5.NF.A.1
South Carolina 5.PAFR.2.1, 5.PAFR.3.1
South Dakota 5.NF.A.1
Tennessee 5.NF.A.1
Texas 111.7.b.3.H, 111.7.b.3.K
Utah 5.NF.1
Vermont 5.NF.A.1
Virginia 5.CE.2a, 5.CE.2b
Washington 5.NF.A.1
West Virginia M.5.11
Wisconsin M.5.NF.A.1

Adding tops and bottoms