Mathematics 2017 GCSE (9-1)

(I have used the Edexcel workbook 2016, by working out their questions, then using their advised methods for papers: )

1) Factors and primes

-HCF AND LCM

When finding the HCF (highest common factor) of 2 numbers: First, you must find the prime factor products of the 2 numbers. For example: 90 and 210

90= 9x10

9= 3 cubed which is 3x3

10= 5x2

So 90=2x3x3x5

210=

10x21

10=5x2

21=3x7

210=2x3x5x7

So,

90=2x3x3x5 &

210=2x3x5x7

HCF= 2x3x5

HCF=30

LCM= HCF x the un-highlighted products

So LCM= 30x3x7

LCM= 630

Example Question:

A rambler's club buys hats in packs of…