Gcf lcm word problems

HCF and LCM & Word Problem Solving Definition of HCF and LCM. How can you tell if a word problem requires you to use Greatest Common Factor or Least Common Multiple to solve?

Prime Factors Wednesday 6 October 2010 Objective Write a number as a product of its prime factors. Find the HCF and LCM of two numbers © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.uk

12 ÷ 2 = 6 12 ÷ 3 = 4 12 ÷ 6 = 2 12 can be divided by 2, 4 and 6 so 12 is not a prime number. 7 ÷ 7 = 1 7 ÷ 1 = 7 Prime Numbers A prime number is a number that can only be divided (exactly) by itself and 1. 7 can only be divided by itself and 1 to give an integer answer. 7 is a prime number © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.uk

Write down the prime numbers between 1 and 40. © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.uk 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Factors Factors are the numbers that multiply together to give a certain number. The factor pairs of 12 are: 1 x 12 = 12 2 x 6 = 12 3 x 4 = 12 4 x 3 = 12 6 x 2 = 12 12 x 1 = 12 © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.uk

Find the Highest Common Factor (HCF) of 36 and 72 1. Find the prime factors of both numbers 36 = 2 x 2 x 3 x 3 72 = 2 x 2 x 2 x 3 x 3 2. Use one of each of the numbers that are in both lists HCF = 2 x 2 x 3 x 3 HCF = 36 © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.uk

Find the Lowest Common Multiple (LCM) of 36 and 90 1. Find the prime factors of both numbers 36 = 2 x 2 x 3 x 3 90 = 2 x 3 x 3 x 5 2. Use one of each of the numbers that are in both lists and all the remaining numbers. LCM = 2 x 3 x 3 x 2 x 5 LCM = 180 © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.uk

1. Find the HCF of 12 and 30. 2. Find the HCF of 54 and 180. 3. Find the LCM of 18 and 30. 4. Find the LCM of 24 and 84. 5. Find the LCM of 54 and 120 6. Find the LCM of 72 and 150 1. 6 2. 18 3. 90 4. 168 5. 1080 6. 5600 © Brain-Cells: E.Resources Ltd. All Rights Reserved 24/11/09 www.brain-cells.co.uk

HCF and LCM Problem Solving ,[object Object],[object Object],[object Object],[object Object]

If it is a HCF Problem ,[object Object],[object Object],[object Object],[object Object]

HCF Example: Applying what we have learned… ,[object Object]

Samantha has two pieces of cloth. One piece is 72 inches wide and the other piece is 90 inches wide. She wants to cut both pieces into strips of equal width that are as wide as possible. How wide should she cut the strips? ,[object Object],[object Object]

[object Object],[object Object],Samantha has two pieces of cloth. One piece is 72 inches wide and the other piece is 90 inches wide. She wants to cut both pieces into strips of equal width that are as wide as possible. How wide should she cut the strips?

HCF Word Problem Solution ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

If it is an LCM Problem ,[object Object],[object Object],[object Object],[object Object]

LCM Example: Applying what we have learned… ,[object Object]

Ben exercises every 12 days and Isabel every 8 days. Ben and Isabel both exercised today. How many days will it be until they exercise together again? ,[object Object],[object Object]

[object Object],[object Object],Ben exercises every 12 days and Isabel every 8 days. Ben and Isabel both exercised today. How many days will it be until they exercise together again?

LCM Word Problem Solution ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

QUIZ Answers… ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Gcf lcm word problems

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