Question

What is the biggest number that can go into 40 and 20

Answer 1

so we find what's called the GCF or greatest common factor
firest we find teh factors and group the like ones

40=2 times 2 times 2 times 5
20=2 times 2 times 5
we see a common set of numbers which is in both which is 2 times 2 times 5=20
biggest number that can go into both 40 and 20=20