HCF LCM Prime Factorisation Worksheet B An animated

HCF & LCM – Prime Factorisation – Worksheet B An animated demonstration for the method is included.

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Find a 1 st common factor for the pair. (start with small prime numbers) Divide by the common factor for the next row. 24 ÷ 2 = 12 42 ÷ 2 = 21 Find a 2 nd common factor for the pair. 2 24 42 3 12 21 4 7 Are there any more common factors? HCF = Product of common factors (column 1) =2× 3=6 LCM = Product of HCF and remainders = 6 × 4 × 7 = 168

Find a 1 st common factor for the pair. Divide by the common factor for the next row. 90 ÷ 5 = 18 75 ÷ 5 = 15 Find a 2 nd common factor for the pair. 5 90 75 3 18 15 6 5 Are there any more common factors? HCF = Product of common factors (column 1) = 5 × 3 = 15 LCM = Product of HCF and remainders = 15 × 6 × 5 = 450

Finding HCF & LCM: Factor Method 1 st Common Factor 2 nd Common Factor 2 3 24 42 12 4 21 7 Remainders (No common factors remain) HCF = Product of common factors (column 1) = 2 × 3 = 6 LCM = Product of HCF and remainders = 6 × 4 × 7 = 168 Using the tables, calculate the HCF and LCM of each pair of numbers. A) 2 5 50 30 25 5 15 3 HCF = LCM = C) 30 HCF = LCM = 28 D) 24 60 HCF = LCM = 240 HCF = LCM = 12 2 2 HCF = LCM = 100 E) B) 140 Construct your own tables to find the HCF and LCM of: F) G) H) I) J) 140 & 40 270 & 225 300 & 420 630 & 700 600 & 480 & 840

Finding HCF & LCM: Factor Method 1 st Common Factor 2 nd 2 3 Common Factor 24 42 Question HCF LCM 12 4 21 7 A 10 130 B 4 84 C 10 300 D 12 120 E 20 1680 Remainders (No common factors remain) HCF = Product of common factors (column 1) = 2 × 3 = 6 LCM = Product of HCF and remainders = 6 × 4 × 7 = 168 Using the tables, calculate the HCF and LCM of each pair of numbers. A) 2 5 50 30 25 5 15 3 HCF = 2 × 5 = 10 LCM = 10 × 5 × 3 = 150 C) 2 5 2 2 12 28 6 3 14 7 HCF = 2 × 2 = 4 LCM = 4 × 3 × 7 = 84 100 30 50 10 15 3 HCF = 2 × 5 = 10 LCM = 10 × 3 = 300 E) B) D) 2 2 3 F 24 60 12 6 2 30 15 5 HCF = 2 × 3 = 12 LCM = 12 × 5 = 120 240 120 60 12 70 35 7 HCF = 2 × 5 = 20 LCM = 20 × 12 × 7 = 1680 Construct your own tables to find the HCF and LCM of: F) G) H) I) J) 140 & 40 270 & 225 300 & 420 630 & 700 600 & 480 & 840 G H I J Half Answers

Finding HCF & LCM: Factor Method 1 st Common Factor 2 nd 2 3 Common Factor 24 42 Question HCF LCM 12 4 21 7 A 10 130 B 4 84 C 10 300 D 12 120 E 20 1680 F 20 280 G 45 1350 H 60 2100 I 70 6300 J 120 16800 Remainders (No common factors remain) HCF = Product of common factors (column 1) = 2 × 3 = 6 LCM = Product of HCF and remainders = 6 × 4 × 7 = 168 Using the tables, calculate the HCF and LCM of each pair of numbers. A) 2 5 50 30 25 5 15 3 HCF = 2 × 5 = 10 LCM = 10 × 5 × 3 = 150 C) 2 5 2 2 12 28 6 3 14 7 HCF = 2 × 2 = 4 LCM = 4 × 3 × 7 = 84 100 30 50 10 15 3 HCF = 2 × 5 = 10 LCM = 10 × 3 = 300 E) B) D) 2 2 3 24 60 12 6 2 30 15 5 HCF = 2 × 3 = 12 LCM = 12 × 5 = 120 240 120 60 12 70 35 7 HCF = 2 × 5 = 20 LCM = 20 × 12 × 7 = 1680 Construct your own tables to find the HCF and LCM of: F) G) H) I) J) 140 & 40 270 & 225 300 & 420 630 & 700 600 & 480 & 840 Answers

Finding HCF & LCM: Factor Method 1 st Common Factor 2 nd Common Factor 2 3 Finding HCF & LCM: Factor Method 24 42 1 st Common Factor 12 4 21 7 2 nd Remainders (No common factors remain) HCF = Product of common factors (column 1) = 2 × 3 = 6 LCM = Product of HCF and remainders = 6 × 4 × 7 = 168 2 5 50 30 25 5 15 3 HCF = LCM = C) 30 HCF = LCM = 28 A) D) 140 24 60 50 30 25 5 15 3 12 4 21 7 Remainders (No common factors remain) C) 100 140 & 40 270 & 225 300 & 420 630 & 700 600 & 480 & 840 E) 12 2 2 28 30 D) 24 60 HCF = LCM = 240 HCF = LCM = B) HCF = LCM = Construct your own tables to find the HCF and LCM of: F) G) H) I) J) 2 5 HCF = LCM = 240 HCF = LCM = 12 2 2 42 Using the tables, calculate the HCF and LCM of each pair of numbers. HCF = LCM = 100 E) B) 24 HCF = Product of common factors (column 1) = 2 × 3 = 6 LCM = Product of HCF and remainders = 6 × 4 × 7 = 168 Using the tables, calculate the HCF and LCM of each pair of numbers. A) Common Factor 2 3 140 Construct your own tables to find the HCF and LCM of: F) G) H) I) J) 140 & 40 270 & 225 300 & 420 630 & 700 600 & 480 & 840

Questions? Comments? Suggestions? …or have you found a mistake!? Any feedback would be appreciated . Please feel free to email: tom@goteachmaths. co. uk