In mathematics number system is primarily divided into real numbers , integers , natural number , whole numbers , rational numbers and irrational numbers. Addition is the only property on numbers which is valid on all the categories of numbers.
Subtraction of two irrational numbers may be a rational number too e.g.
√2−√2=02-2=0
which is a rational number. Product of two irrational numbers can be rational or irrational number. For example √2 √3 = √6 ∈ Qc and √2 √2 = 2 ∈ Q.
Let the number of times (4+8) to be added be n.
Therefore
n(4+8)=40
⇒ n(12)=40
⇒ n = 40/12
⇒ n = 3.5
Hence we have to add (4+8) at least 4 times to get 40.
