Summary: Finding Multiples and Factors
Key Concepts
Divisibility Tests | |
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A number is divisible by | |
if the last digit is or | |
if the sum of the digits is divisible by | |
if the last digit is or | |
if divisible by both and | |
if the last digit is |
- Factors If , then and are factors of , and is the product of and .
- Find all the factors of a counting number.
- Divide the number by each of the counting numbers, in order, until the quotient is smaller than the divisor.
- If the quotient is a counting number, the divisor and quotient are a pair of factors.
- If the quotient is not a counting number, the divisor is not a factor.
- List all the factor pairs.
- Write all the factors in order from smallest to largest.
- Divide the number by each of the counting numbers, in order, until the quotient is smaller than the divisor.
- Determine if a number is prime.
- Test each of the primes, in order, to see if it is a factor of the number.
- Start with and stop when the quotient is smaller than the divisor or when a prime factor is found.
- If the number has a prime factor, then it is a composite number. If it has no prime factors, then the number is prime.
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