Foundation November 2020 Paper 2 Q24
24 Work out the highest common factor (HCF) of 75 and 105 [2 marks]
| Answer | Mark | Comments |
|---|---|---|
| 15 | B2 | B1 answer 3 or answer 5 or answer 3 \((\times)\) 5 or (75 =) 3 \((\times)\) 5 \((\times)\) 5 or (75 =) 3 \((\times)\) \(5^2\) or (105 =) 3 \((\times)\) 5 \((\times)\) 7 or (1) 3 5 15 25 (75) or (1) 3 5 7 15 21 35 (105) |
Additional guidance
| NB 15 from \(3 + 5 + 7\) does not score unless working for B1 seen elsewhere | |
| Prime factor responses for B1 may be seen in repeated division, on a factor tree or in a Venn diagram eg1 3 5 5 in repeated division or factor tree for 75 eg2 3 5 7 inside one circle of a Venn diagram eg3 3 5 inside the intersection of a Venn diagram | B1 B1 B1 |
| For products of prime factors, repeated division, factor trees and Venn diagrams, ignore inclusion of factors of 1 | |
| A repeated division needs to reach the final prime factor but does not need to reach 1 | |
| B1 can be awarded even if LCM is subsequently worked out | |
| List of factors may be seen as factor pairs |