Q1
What is a rational number?
AOne expressible as p/q
BOne that cannot be expressed as p/q
COnly a whole number
DOnly a negative number
ICSEClass 9 (ICSE)MathematicsCh 1 · Topic 1
Rational and Irrational Numbers
Rational numbers can be expressed as p/q, while irrational numbers cannot, like √2 or π, and both types together form real numbers.
Core concept
Rational numbers, like 3/4 or 5, have terminating or repeating decimal expansions when converted to decimal form.
How it works
Irrational numbers, like √2 or π, have non-terminating, non-repeating decimal expansions that continue infinitely without pattern.
Why it matters
Together, rational and irrational numbers form the set of real numbers, which can be represented on the number line.
Key detail
Understanding this distinction helps us classify numbers correctly and work with more complex numbers in advanced algebra and geometry.
Exam highlight
Key diagram
Keywords worth remembering
Trending
rational and irrational numbersicse class 9
Most searched
ICSE class 9 rational and irrational numbers
Quick revision
Study resources
Notes & downloads
Quick notes
• Rational numbers can be written as p/q.
• They have terminating or repeating decimals.
• Irrational numbers cannot be written as p/q.
• Examples: √2, π.
• They have non-terminating, non-repeating decimals.
• Rational + irrational numbers form real numbers.
• Real numbers can be shown on a number line.
• This distinction is key for advanced maths.