If your child needs math practice, click here.

For sample problems, click here.
Here are some tips for Prime Factoring, which aligns with New York state standards:

Prime Factoring

Factoring numbers into their prime numbers requires good division skills.

Here are some divisibility rules that should help:
Divisibility by 2: If the number ends in 0,2,4,6, or 8, it is divisible by 2.
Divisibility by 3: If the sum of the digits is divisible by 3, the number is divisible by 3.  
   Example: 27 is divisible by 3 because 2 + 7 = 9, which is divisible by 3.
Divisibility by 5: If the number ends in 0 or 5, it is divisible by 5.

Factoring example 1:
Factor 24:
24 is divisible by 2, so we now have 2*12
12 is divisible by 2, so we now have 2*2*6
6 is divisible by 2, so we now have 2*2*2*3, which is the final answer.

Factoring example 2:
Factor 47:
47 is not divisible by 2 because it is not an even number.
47 is not divisible by 3 because 4+7=11 is not divisible by 3
47 is not divisible by 5 because it does not end in 0 or 5
47 is not divisible by 7 because we know that 7*6=42 and 7*7=49
Therefore, 47 is a prime number, so our answer is simply 47.

Factoring example 3:
Factor 117:
111 is divisible by 3 because 1+1+1=3, which is divisible by 3, giving us 3*39
39 is also divisible by 3, so we now have 3*3*13, which is our final answer.

List of prime numbers up to 150:
If you want to be really fast at factoring, you might want to memorize these
numbers:
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67,
71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149

Copyright Accurate Learning Systems Corporation 2008.
MathScore is a registered trademark.