What this lesson shows
Exactly two factors is prime. More is composite. Divisibility rules speed it up.
The worked example
The lesson works this one step by step: 39. Then your kid tries one like it on paper.
The steps
- Prime: exactly two factors
- Composite: more than two
- Rules for 2, 3, and 5 find factors fast
Helping at home
Look for a factor other than 1 and the number. Even means 2 is a factor. Digits that add to a multiple of 3 mean 3 is. Ending in 0 or 5 means 5 is. Exactly two factors: prime. More: composite.
If your kid gets stuck
Try the rules for 2, 3, and 5 first.
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 4.OA.B.4
Find all factor pairs for a whole number in the range 1-100. Recognize that a whole number is a multiple of each of its factors. Determine whether a given whole number in the range 1-100 is a multiple of a given one-digit number. Determine whether a given whole number in the range 1-100 is prime or composite.
Matches standards in 48 statesSee each state's code
- Alabama MA19.4.4a, MA19.4.4b
- Alaska 4.OA.4
- Arizona 4.OA.B.4, 5.OA.B.4
- Arkansas 4.CAR.1
- California 4.OA.B.4
- Colorado 4.OA.B.4
- Connecticut 4.OA.B.4
- Delaware 4.OA.B.4
- District of Columbia 4.OA.B.4
- Florida MA.4.AR.3.1
- Georgia 4.PAR.3.3, 4.PAR.3.4
- Hawaii 4.OA.B.4
- Idaho 4.OA.B.4.a, 4.OA.B.4.b, 4.OA.B.4.c
- Illinois 4.OA.B.4
- Indiana 4.CA.4
- Iowa 4.OA.B.4
- Kansas 4.OA.4
- Kentucky KY.4.OA.4.a, KY.4.OA.4.b, KY.4.OA.4.c, KY.4.OA.4.d
- Louisiana 4.OA.B.4.a, 4.OA.B.4.b, 4.OA.B.4.c, 4.OA.B.4.d
- Maine 4.OA.B.4
- Maryland 4.NOS.C.8.a, 4.NOS.C.8.b, 4.NOS.C.8.c, 4.NOS.C.8.d
- Massachusetts 4.OA.B.4
- Michigan 4.OA.B.4
- Mississippi 4.OA.4
- Missouri 4.RA.B.4, 4.RA.B.5
- Montana MT.4.OA.4, 4.D1.6, 4.D2.3
- Nebraska 4.N.4.a, 4.N.4.b
- Nevada 4.OA.B.4
- New Hampshire 4.OA.B.4
- New Jersey 4.OA.B.4
- New Mexico 4.OA.B.4
- New York NY-4.OA.4
- North Carolina NC.4.OA.4.a, NC.4.OA.4.b, NC.4.OA.4.c
- North Dakota 4.AR.OA.4, 5.AR.OA.4
- Ohio 4.OA.4
- Oregon 4.OA.B.4
- Pennsylvania CC.2.2.4.A.2
- Rhode Island 4.OA.B.4
- South Carolina 5.PAFR.3.2, 4.PAFR.3.1, 3.PAFR.2.4
- South Dakota 4.OA.B.4.a, 4.OA.B.4.b, 4.OA.B.4.c, 4.OA.B.4.d
- Tennessee 4.OA.B.4
- Texas 111.7.b.4.A
- Utah 4.OA.4
- Vermont 4.OA.B.4
- Virginia 4.CE.2e, 4.CE.2f, 5.NS.2a, 5.NS.2b
- Washington 4.OA.B.4
- West Virginia M.4.4
- Wisconsin M.4.OA.B.4