Adding fractions with unlike denominators: 5th grade math lesson

What this lesson shows

3/4 + 5/8: rename fourths as eighths, so 6/8 + 5/8 = 11/8.

The worked example

The lesson works this one step by step: 3/4 + 5/8. Then your kid tries one like it on paper.

The steps

Estimate the sum
Rename to the same parts
Add the tops, keep the parts

Helping at home

Estimate first: is each fraction more or less than a half? Then rename the fraction with the bigger parts so both have the same parts, multiplying its top and bottom by the same number. Add the tops; the bottom stays. No simplifying needed.

If your kid gets stuck

Estimate. Rename to the same parts, then add 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 fractions with unlike denominators