How do I find the highest common factor of two numbers?
The factors of a number are all the numbers that divide into it, so the HCF of two numbers is the highest number that is a factor of both numbers. I'd work it out by create a list of all of the prime factors of the two numbers, which you could find using a tree (like this: use whiteboard). Find all of the common factors, i.e. the numbers which are in both lists. If you multiply all the common factors, you will have the highest common factor.
As an example, the prime factors of 72 are 2, 2, 2, 3, 3 and the prime factors of 84 are 2, 2, 3, and 7. The common factors are 2, 2, and 3. 2 x 2 x 3 = 12. The highest common factor of 72 and 84 is therefore 12.
OB
Related Maths GCSE answers
All answers ▸Gavin, Harry and Isabel each earn the same salary. Gavin saves 28% of his salary. Harry spends 3/4 of his salary and saves the rest. The amount Isabel saves:The amount she spends=3:7. Who saves the most?
A football pitch has a length of the xm. Its width is 25m shorter than the length. The area of the pitch is 2200m2. Show that x2 - 25x - 2200 =0 and work out the length of the football pitch.
Factorise x^2 -7x+10, and hence solve x^2-7x+10=0
The formula for finding the circumference of a circle is Equation: C = 2(pi)r . What can we do if we know the circumference but want to know the radius?