Change both parts, not one: 4th grade math lesson

What this lesson shows

Fixes a mistake

3/4 is not 3/8. Multiply the top and the bottom by the same number.

The worked example

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

The steps

Same-size bars, same amount?
Cut every part again
Change the top and the bottom

Helping at home

Draw both fractions as bars the same size and ask if they show the same amount. Cut each part to make the new parts, then count the shaded ones. Top and bottom grow by the same times.

If your kid gets stuck

Whatever the bottom is multiplied by, the top is too.

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 4.NF.A.1
Explain why a fraction a/b is equivalent to a fraction (n × a)/(n × b) by using visual fraction models, with attention to how the number and size of the parts differ even though the two fractions themselves are the same size. Use this principle to recognize and generate equivalent fractions.

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

Alabama MA19.4.13a
Alaska 4.NF.1
Arizona 4.NF.A.1 *
Arkansas 4.NPV.8
California 4.NF.A.1
Colorado 4.NF.A.1
Connecticut 4.NF.A.1
Delaware 4.NF.A.1
District of Columbia 4.NF.A.1
Florida MA.4.FR.1.3
Georgia 4.NR.4.1
Hawaii 4.NF.A.1
Idaho 4.NF.A.1
Illinois 4.NF.A.1
Indiana 4.NS.3
Iowa 4.NF.A.1
Kansas 4.NF.1
Kentucky KY.4.NF.1.a, KY.4.NF.1.b
Louisiana 4.NF.A.1
Maine 4.NF.A.1
Maryland 4.NOS.D.9.a, 4.NOS.D.9.b
Massachusetts 4.NF.A.1
Michigan 4.NF.A.1
Minnesota 4.1.2.1
Mississippi 4.NF.1
Missouri 4.NF.A.1, 4.NF.A.2, 5.NF.B.5.d
Montana MT.4.NF.1, 4.D1.7, 4.D1.25, 4.D3.2
Nebraska 4.N.2.b
Nevada 4.NF.A.1
New Hampshire 4.NF.A.1
New Jersey 4.NF.A.1
New Mexico 4.NF.A.1
New York NY-4.NF.1
North Carolina NC.4.NF.1
North Dakota 4.NO.NF.2, 4.NO.NF.3, 4.NO.NF.4
Ohio 4.NF.1
Oklahoma 4.N.3.1
Oregon 4.NF.A.1
Pennsylvania CC.2.1.4.C.1
Rhode Island 4.NF.A.1
South Carolina 4.NR.2.3, 5.PAFR.3.2
South Dakota 4.NF.A.1
Tennessee 4.NF.A.1
Texas 111.6.b.3.C
Utah 4.NF.1
Vermont 4.NF.A.1
Virginia 4.NS.3e
Washington 4.NF.A.1
West Virginia M.4.12
Wisconsin M.4.NF.A.1
Wyoming 4.NF.1

Change both parts, not one