Factors and Multiples
Below is an applet to help with identifying factors and multiples. There also follow a set of questions; you can use the applet to help you.
1)
How many numbers between 1 and 20 have 3 as a factor?
2)
Which number has 1 factor?
3)
Which of the following are multiples of 10?
4)
A number between 10 and 19 has an odd number of factors. Which number is it?
5)
Identify the relationship between factors and multiples.
6)
You have been told that 143 = 11 × 13. Which of the following are true?
Finding Primes Activity (Sieve of Eratosthenes)
There is a way to find prime numbers that was used by the ancient Greeks. See if you can follow the reasoning.
A Visual Method for Finding Prime Numbers
Question 1)
We crossed out the number 1 in Step 1. How do we know that 1 is not a prime number?
Question 2)
In Step 3, we crossed out the multiples of 2 (that were bigger than 2). How do we know these numbers are not prime?
Question 3)
List all of the prime numbers between 1 and 100.
Question 4)
A lot of the numbers ending with the digit 1 are prime. However, 51 is not a prime number.[br]List all the factors of 51 and explain why it is not a prime number.
Question 5)
In our example, we could stop with the multiples of 7. Can you explain why?[br](Hint: It depends on the size of the grid).