Flashcards
prime numbers, factors and multiples
Cards in this deck (10)
- 1what is a prime number?A prime number is a number which is only divisible by and itself.
Eg: 2 is a prime number because it only divides into 2 and 1 - 2what are the first ten prime numbers?the first ten prime numbers are: 2,3,5,7,11,13,17,19,23,29
- 3what are the prime numbers between 50 and 60?53 & 59
- 4what are factor pairs?Factors are often given as pairs of numbers, which multiply together to give the original number. These are called factor pairs.
- 5what are the factor pairs of 20?1 & 20
2 & 10
4 & 5 - 6what are factor trees?It is often useful to write a number as the product of its prime factors. This can be done by listing the factor pairs as successive branches in a factor tree. The branches continue to expand until all the factors are prime numbers. The final answer is the product of the prime numbers displayed at the end of these branches
- 7what is the highest common factor (HCF)?The factors of a number are any numbers that divide into it exactly.
Eg: the factors of 12 are 1,2,3,4,6,12 - 8what is the HCF of 16 and 40?the factors of 16 are 1,2,4,8,16
the factors of 40 are 1,2,4,5,8,10,20,40
so the highest common factor of 16 and 40 is 8 - 9what is the lowest common multiple (LCM)?The multiples of a number are all the numbers that it will divide into.
Eg: the multiples of 4 are 4,8,12,16,20,24,28,30,32,36... - 10what is the LCM of 5 and 8?The multiples of 5 are 5 ,10, 15, 20, 25,
30, 35, 40
The multiples of 8 are 8, 16 24, 32, 40, 48, 56
So the LCM of 5 and 8 is 40.