What this lesson shows
10 ones bundle into 1 ten, so the total never changes. Check one sum by adding tens first, then ones first.
The worked example
The lesson works this one step by step: 38 + 45 = □. Then your kid tries one like it on paper.
The steps
- Bundle 10 ones into a ten
- Add tens first
- Add ones first
- Both make the same total
Helping at home
Show each number in tens and ones. Bundle 10 ones into a ten: nothing is added or taken away. Then add tens first, and again ones first. Both ways make the same total.
If your kid gets stuck
Add it both ways.
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.
Standards
- Common Core 2.NBT.B.9
Explain why addition and subtraction strategies work, using place value and the properties of operations.
Matches standards in 47 statesSee each state's code
- Alabama MA19.2.14
- Alaska 2.NBT.5, 2.NBT.9
- Arizona 2.NBT.B.9
- California 2.NBT.B.9
- Colorado 2.NBT.B.9
- Connecticut 2.NBT.B.9
- Delaware 2.NBT.B.9
- District of Columbia 2.NBT.B.9
- Florida MA.2.NSO.2.3
- Georgia 2.NR.2.3
- Hawaii 2.NBT.B.9
- Idaho 2.NBT.B.5, 2.NBT.B.9
- Illinois 2.NBT.B.9
- Iowa 2.NBT.B.5, 2.NBT.B.9
- Kansas 2.NBT.5, 2.NBT.9
- Kentucky KY.2.NBT.9
- Louisiana 2.NBT.B.9
- Maine 2.NBT.B.9
- Maryland 2.NOS.C.8.a, 2.NOS.C.8.c, 2.NOS.C.9.d
- Massachusetts 2.NBT.B.9
- Michigan 2.NBT.B.9
- Minnesota 2.1.2.4
- Mississippi 2.NBT.9
- Missouri 2.NBT.B.6
- Montana MT.2.NBT.5, MT.2.NBT.9
- Nebraska 2.N.4.b
- Nevada 2.NBT.B.9
- New Hampshire 2.NBT.B.9
- New Jersey 2.NBT.B.9
- New Mexico 2.NBT.B.9
- New York NY-2.NBT.9
- North Carolina NC.2.NBT.5.b
- North Dakota 2.NO.NBT.3, 2.NO.NBT.4, 2.AR.OA.2
- Ohio 2.NBT.9
- Oklahoma 2.N.2.4
- Oregon 2.NBT.B.9
- Rhode Island 2.NBT.B.9
- South Carolina 2.PAFR.1.1
- South Dakota 2.NBT.B.9
- Tennessee 2.NBT.B.5, 2.NBT.C.7
- Texas 111.4.b.4.B
- Utah 2.NBT.9
- Vermont 2.NBT.B.9
- Virginia 2.CE.1b, 2.CE.1f
- Washington 2.NBT.B.9
- West Virginia M.2.14
- Wisconsin M.2.NBT.B.9, M.2.NBT.B.5
More in this unit
- Rounding to the nearest ten
- Which two tens?
- Look at the ones
- Halfway rounds up
- Adding by jumps
- Adding tens and ones
- Ten ones make a ten
- Subtracting tens and ones
- Trade a ten for ten ones
- Not always small from big
- Count up to subtract
- Two-step word problems
- A story for an equation
- Add four numbers
- Estimate, then add