Line up the decimal points: 4th grade math lesson

What this lesson shows

Fixes a mistake

30.1 + 2.74: tenths go with tenths. Write 30.10 to see it.

The worked example

The lesson works this one step by step: 30.1 + 2.74. Then your kid tries one like it on paper.

The steps

Points over points
Fill empty places with 0
Work from the right
Check with an estimate

Helping at home

Write the numbers one under the other with the points lined up, never the last digits. Fill any empty place with a 0, so 30.1 becomes 30.10, then work from the right. A whole number like 8 has its point after the ones: 8.00.

If your kid gets stuck

Line up the points, then fill the empty places with 0.

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.NBT.B.7
Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

Matches a standard in all 50 states and DCSee each state's code

Alabama MA19.5.8a, MA19.5.8b
Alaska 5.NBT.7
Arizona 5.NBT.B.7 *
Arkansas 5.CAR.3, 5.CAR.4
California 5.NBT.B.7
Colorado 5.NBT.B.7
Connecticut 5.NBT.B.7
Delaware 5.NBT.B.7
District of Columbia 5.NBT.B.7
Florida MA.5.NSO.2.3, MA.5.NSO.2.4, MA.5.M.2.1, MA.4.NSO.2.7
Georgia 5.NR.4.4
Hawaii 5.NBT.B.7
Idaho 5.NBT.A.7.a, 5.NBT.A.7.b
Illinois 5.NBT.B.7
Indiana 5.CA.9, 5.CA.10
Iowa 5.NBT.B.7
Kansas 5.NBT.7
Kentucky KY.5.NBT.7.a, KY.5.NBT.7.b
Louisiana 5.NBT.B.7
Maine 5.NBT.B.7
Maryland 5.NOS.B.4.a, 5.NOS.B.5.a, 5.NOS.B.6.b, 5.NOS.B.6.c, 5.NOS.B.6.d, 5.NOS.B.7.a, 5.NOS.B.7.b, 5.NOS.B.7.c, 5.NOS.B.7.d, 5.NOS.B.7.e
Massachusetts 5.NBT.B.7
Michigan 5.NBT.B.7
Minnesota 5.1.1.3, 5.1.3.1, 5.1.3.2, 5.1.3.4
Mississippi 5.NBT.7
Missouri 5.NBT.A.6, 5.NBT.A.7, 5.NBT.A.8, 5.NF.B.4, 5.RA.C.5
Montana MT.5.NBT.7, 5.D1.11, 5.D1.12, 5.D1.13, 5.D2.11, 5.D2.12
Nebraska 5.N.3.g, 5.A.1.c
Nevada 5.NBT.B.7
New Hampshire 5.NBT.B.7
New Jersey 5.NBT.B.7
New Mexico 5.NBT.B.7
New York NY-5.NBT.7
North Carolina NC.5.NBT.7.a, NC.5.NBT.7.b, NC.5.NBT.7.c, NC.5.NBT.7.d
North Dakota 5.NO.NBT.5
Ohio 5.NBT.7.a, 5.NBT.7.b, 5.NBT.7.c
Oklahoma 5.N.2.1, 5.N.3.2, 5.N.3.3
Oregon 5.NBT.B.7
Pennsylvania CC.2.1.5.B.2
Rhode Island 5.NBT.B.7
South Carolina 5.PAFR.1.4, 5.PAFR.1.3
South Dakota 5.NBT.B.7.a, 5.NBT.B.7.b
Tennessee 5.NBT.B.7
Texas 111.6.b.4.A, 111.7.b.3.A, 111.7.b.3.D, 111.7.b.3.E, 111.7.b.3.F, 111.7.b.3.G, 111.7.b.3.K
Utah 5.NBT.7
Vermont 5.NBT.B.7
Virginia 4.CE.4a.i, 4.CE.4a.ii, 4.CE.4b, 5.CE.3a, 5.CE.3b.i, 5.CE.3b.ii, 5.CE.3b.iii, 5.CE.3c.i, 5.CE.3c.ii, 5.CE.3c.iii, 5.CE.3c.iv, 5.CE.3d, 5.CE.3e
Washington 5.NBT.B.7
West Virginia M.5.10
Wisconsin M.5.NBT.A.4, M.5.NBT.B.7
Wyoming 5.NBT.7

Line up the decimal points