Sets of Numbers

A Grade 8 Mathematics topic: «Sets of Numbers» (Chapter 1 «Numbers», 1.1, pp. 7–11, Toh Tin Lam). The aim of the lesson is to classify numbers. 1, 2, 3, 4, 5, … are natural numbers. The integers include the natural numbers, 0 and the negative numbers. Numbers written in the form a/b are called rational (3 = 3/1, and 0.7 = 7/10 is rational too). Numbers that cannot be written as a/b are irrational; the best known is π = 3.1415926…, while 22/7 is an approximate value of it. The sets sit inside one another: natural ⊂ integer ⊂ rational.