Compare rational numbers

Key notes:

🔢 What are Rational Numbers?

  • A rational number is any number that can be written as a fraction:
    👉 a/b, where a and b are integers and b ≠ 0
  • Examples: 1/2, -3/4, 5, 0, -7/1

📏 Convert to Same Form Before Comparing

To compare rational numbers, convert them into:

✔️ Fractions

✔️ Decimals

✔️ Like denominators

Example:
Compare 2/3 and 3/5 → Make denominators same or convert to decimals.


🟰 Use Common Denominators

🌟 Rule: When denominators are the same,
➡️ The number with the bigger numerator is greater.
Example:

  • 7/12 > 5/12 👍

💡 Use Number Line

  • Numbers on the right 👉 are greater than numbers on the left 👈.
  • Example:
    • −2 is to the right of −5, so −2 > −5 😊

🔍 Compare Using Decimals

Convert both numbers into decimals for easy comparison.
Example:

  • 1/4 = 0.25
  • 2/5 = 0.40
    So, 2/5 > 1/4 ✔️

➕➖ Be Careful with Negative Rational Numbers

💥 Rule:

  • The rational number closer to zero is greater when negative.
    Example:
  • −1/3 > −1/2
    Because −1/3 is closer to 0.

🔢 Cross Multiplication Method

Use when denominators are different:
Compare a/b and c/d
👉 Cross multiply: a × d and b × c

  • If a × d > b × c, then a/b > c/d

Example:
Compare: 3/4 and 5/8

  • 3 × 8 = 24
  • 4 × 5 = 20
    ➡️ 24 > 20 so 3/4 > 5/8 🎉

🎯 Remember the Order

👉 Smallest → Largest
👉 Negative < Zero < Positive

Example order:

  • −3/2, −1/4, 0, 2/3, 5/4

🌈 Summary Chart

MethodWhen to UseEmoji
Common denominatorComparing fractions
Number lineVisual comparison📉
DecimalsEasy comparison🔢
Cross multiplicationFast for unlike denominators✖️

Learn with an example

Which sign makes the statement true?

-8 ____ -1/2

  • Remember that when comparing negative numbers, larger numbers like 8 (if you ignore the minus sign) are less than smaller numbers like 1/2.
  • So: -8 < -1/2

Which sign makes the statement true?

-2 3/8 _____ 0

  • A negative number like -2 3/8 is always less than zero.
  • So: -2 3/8 < 0

Which sign makes the statement true?

0 ____ -5 5/8.

A negative number like -5 5/8 is always less than zero.

So: 0 > – 5 5/8

Let’s practice!🖊️