What this lesson shows
Fixes a mistake
18 − □ = 14: is it 8 or 4? Put each back in. Only 18 − 4 makes 14.
The worked example
The lesson works this one step by step: 18 − □ = 14. Then your kid tries one like it on paper.
The steps
- Put the guess back
- Does it match?
- Keep the one that matches
Helping at home
After each answer, write it in the box and work the problem out again. If it matches, it is right. If not, try again.
If your kid gets stuck
Put your answer back in to check.
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 1.OA.D.8
Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 = _ - 3, 6 + 6 = _.
Matches standards in 46 statesSee each state's code
- Alabama MA19.1.8
- Alaska 1.OA.8
- Arizona 1.OA.D.8
- Arkansas 1.CAR.9
- California 1.OA.D.8
- Colorado 1.OA.D.8
- Connecticut 1.OA.D.8
- Delaware 1.OA.D.8
- District of Columbia 1.OA.D.8
- Florida MA.1.AR.2.3
- Georgia 1.NR.2.6
- Hawaii 1.OA.D.8
- Idaho 1.OA.D.8
- Illinois 1.OA.D.8
- Iowa 1.OA.D.8
- Kansas 1.OA.8
- Kentucky KY.1.OA.8
- Louisiana 1.OA.D.8
- Maine 1.OA.D.8
- Maryland 1.AT.A.3
- Massachusetts 1.OA.D.8
- Michigan 1.OA.D.8
- Minnesota 1.2.2.3
- Mississippi 1.OA.8
- Missouri 1.RA.A.4
- Montana MT.1.OA.9
- Nebraska 1.N.5.c
- Nevada 1.OA.D.8
- New Hampshire 1.OA.D.8
- New Jersey 1.OA.D.8
- New Mexico 1.OA.D.8
- New York NY-1.OA.8
- North Carolina NC.1.OA.8
- Ohio 1.OA.8
- Oklahoma 3.A.2.1
- Oregon 1.OA.D.8
- Rhode Island 1.OA.D.8
- South Carolina 2.PAFR.1.7, 1.PAFR.1.6
- South Dakota 1.OA.D.8
- Tennessee 1.OA.D.8
- Texas 111.3.b.3.B, 111.3.b.5.F
- Utah 1.OA.8
- Vermont 1.OA.D.8
- Virginia 1.CE.1g, 2.CE.1g
- Washington 1.OA.D.8
- West Virginia M.1.8