Draw the factor tree of 90:
90
10 9
5 2 3 3
Circle the prime numbers after you have finished the factor tree. I have put them in a different colour.
90 = 2 x 3 x 3 x 5
2, 3, 3 and 5 are the product of prime numbers. You could also have:
90 = 2 x 3squared x 5
HCF
This is the Highest Common Factor. To find the HCF of 90 and 252 you have to do the factor trees first.
90 252
10 9 28 9
5 2 3 3 7 4 3 3
2 2
90 = 2 x 3 x 3 x 5
252 = 2 x 2 x 3 x 3 x 7
If a number appears in the 90 row and the 252 row you cross one of them out and circle one.
If a number is suppose to be circled it will be in red, if a number is suppose to be crossed out it will be in purple and if a number doesn't appear in both rows it will be in blue.
90 = 2 x 3 x 3 x 5
252 = 2 x 2 x 3 x 3 x 7
To find the HCF you times all the numbers that are circled together.
2 x 3 x 3 = 18
HCF = 18
LCM
This it the Lowest Common Multiple. We are going to find the LCM from the numbers before; 90 and 252. We need to have the numbers when they are circled or crossed off or nothing.
90 = 2 x 3 x 3 x 5
252 = 2 x 2 x 3 x 3 x 7
LCM = (the numbers that are circled and any other numbers that don't appear twice times together)
LCM = 2 x 3 x 3 x 5 x 2 x 7
= 2 x 2 x 3 x 3 x 5 x 7
= 2squared x 3squared x 5 x 7
= 1260
Questions
1. What is the HCF and LCM of 315 and 660?
2. What is the HCF and LCM of 250 and 480?
90
10 9
5 2 3 3
Circle the prime numbers after you have finished the factor tree. I have put them in a different colour.
90 = 2 x 3 x 3 x 5
2, 3, 3 and 5 are the product of prime numbers. You could also have:
90 = 2 x 3squared x 5
HCF
This is the Highest Common Factor. To find the HCF of 90 and 252 you have to do the factor trees first.
90 252
10 9 28 9
5 2 3 3 7 4 3 3
2 2
90 = 2 x 3 x 3 x 5
252 = 2 x 2 x 3 x 3 x 7
If a number appears in the 90 row and the 252 row you cross one of them out and circle one.
If a number is suppose to be circled it will be in red, if a number is suppose to be crossed out it will be in purple and if a number doesn't appear in both rows it will be in blue.
90 = 2 x 3 x 3 x 5
252 = 2 x 2 x 3 x 3 x 7
To find the HCF you times all the numbers that are circled together.
2 x 3 x 3 = 18
HCF = 18
LCM
This it the Lowest Common Multiple. We are going to find the LCM from the numbers before; 90 and 252. We need to have the numbers when they are circled or crossed off or nothing.
90 = 2 x 3 x 3 x 5
252 = 2 x 2 x 3 x 3 x 7
LCM = (the numbers that are circled and any other numbers that don't appear twice times together)
LCM = 2 x 3 x 3 x 5 x 2 x 7
= 2 x 2 x 3 x 3 x 5 x 7
= 2squared x 3squared x 5 x 7
= 1260
Questions
1. What is the HCF and LCM of 315 and 660?
2. What is the HCF and LCM of 250 and 480?