Factors and primes Flashcards
1
Q
What is the highest common factor of 2 numbers?
A
the highest factor that is a factor of both numbers
2
Q
What is the lowest common multiple of two numbers?
A
the lowest number that is a multiple of both numbers
for each different factor in both numbers, take the ones with the highest powers
e.g.
if number x = 2[9] x 3
number y = 2[7] x 3[2] x 7
LCM = 2[9] x 3[2] x 7
3
Q
Prime factors
Use a factor tree to write 84 as a product of its prime factors
A
84 = 2 x 42 42 = 6 x 7 6 = 3 x 2
84 = 2 x 7 x 3 x 2 84 = 2² x 3 x 7
4
Q
Write 108 as the product of its prime factors. Give your answer in index form.
A
108 = 2 x 54 54 = 6 x 9 6 = 2 x 3 9 = 3 x 3
108 = 2 x 2 x 3 x 3 x 3 = 2² x 3³
5
Q
Work out the HCF of 108 and 24
A
108 = 2 x 2 x 3 x 3 x 3 24 = 2 x 2 x 2 x 3
HCF is 2 x 2 x 3 = 12
6
Q
Work out the LCM of 108 and 24
A
LCM = 12 x 3 x 3 x 2 = 216
