Which number is prime? 4 , 9, 21 , 23
2 answers:
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Answer: 1, 2, 5, and 10
Step-by-step explanation: To find the factors of 10, begin by dividing 10 by 1 which gives us 10. This tells us that 1 and 10 are factors of 10. Next, divide 10 by 2 which gives us 5. This tells us that 2 and 5 are also factors of 10. Next, divide 10 by 3. Notice that 10 doesn't divide evenly by 3 so 3 is not a factor of 10. Next, divide 10 by 4. Since 10 doesn't divide evenly by 4, then 4 is not a factor of 10. Next, divide 10 by 5 which gives us 2. This tells us that 5 and 2 are factors of 10 but notice that we already know that 5 and 2 are factors of 10. This means that 5 and 2 are repeat factors.
There is no need to repeat factors that we already know. In fact, as we are writing the factors of a number, it's important to understand that once we hit repeat factors, all other factors that we try will also repeat.
So here, dividing by anything greater than 5 will give us factors that we already know so we can stop here.
This means that the factors of 10 are 1, 2, 5, and 10.
