Chapter 1: Rational Numbers
5 lessons
A rational number is any number that can be written as p/q, where p and q are integers and q is not zero — which quietly includes every whole number, fraction and integer a student has used up to this point. Rational Numbers opens Class 8 by bringing all of them under one system, with one shared set of rules for addition, subtraction, multiplication and division.
Why it's first
Almost every later chapter assumes a student can add, subtract and multiply rational numbers — including negative ones — without hesitation. Linear equations, algebraic expressions, and the number-based questions buried inside geometry and proportion chapters all lean on this fluency being automatic by the time they arrive.
The most common slip is a sign error when subtracting a negative number — forgetting that subtracting a negative is the same as adding its positive, so −3/4 − (−2/3) actually becomes −3/4 + 2/3, not −3/4 − 2/3. Working with a common denominator (12 in this case) before combining the numerators avoids a second, equally common error: adding numerators and denominators separately without converting first.