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

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

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

2. What is the HCF and LCM of 250 and 480?

__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?