Add and subtract rational numbers

Key notes:

๐Ÿ”ข What Are Rational Numbers?

  • Rational numbers are numbers that can be written as a fraction ๐Ÿฅง
  • Example: 1/2, -3/4, 5, -8, 0.25 ( = 1/4 )
  • They include positive, negative, fractions, and decimals! ๐ŸŒŸ

โž• Adding Rational Numbers with the Same Sign

Add normally and keep the same sign โœ”๏ธ

Example:

  • 3/5 + 2/5 = 5/5 = 1 ๐Ÿ˜„
  • -4 + -2 = -6

๐Ÿ’ก Same side = team up! ๐Ÿค


๐Ÿ”„ Adding Rational Numbers with Different Signs

Subtract the smaller value from the bigger value

Keep the sign of the larger number

Example:

  • 7 – 10 = -3
  • -5 + 12 = 7

๐Ÿ’ก Opposites try to cancel each other! โšกโšก


โž– Subtracting Rational Numbers

Change subtraction to addition of the opposite โœจ

Example:

  • 4 – 7 = 4 + (-7) = -3
  • -3 – 5 = -3 + (-5) = -8

๐Ÿ’ก Subtracting becomes adding the opposite! ๐Ÿ”


๐Ÿฐ Adding & Subtracting Fractions

๐Ÿ“Œ If denominators are the same:

Add/subtract numerators only!

  • 3/8 + 2/8 = 5/8
  • 7/9 – 4/9 = 3/9 = 1/3

๐Ÿ“Œ If denominators are different:

Find LCM (Least Common Multiple) ๐ŸŽฏ

Convert to equivalent fractions

Add/subtract numerators

  • 1/4 + 1/6 โ†’ LCM = 12
  • 3/12 + 2/12 = 5/12

๐ŸงŠ Adding & Subtracting Decimals

Line up the decimal points

Add or subtract normally

  • 3.75 + 2.1 = 5.85
  • 6.4 – 3.25 = 3.15

๐Ÿ–Š๏ธ Keep decimals in the right place! ๐Ÿ“


๐ŸŽฏ Opposites and Zero Pair

A number and its opposite always add to 0

  • 5 + (-5) = 0
  • -8 + 8 = 0

๐Ÿ’ฅ They cancel each other! ๐Ÿšซ


๐Ÿงฎ Key Rule to Remember

โœ”๏ธ Addition โ†’ Follow sign rules
โœ”๏ธ Subtraction โ†’ Add the opposite
โœ”๏ธ Fractions โ†’ Use LCM
โœ”๏ธ Decimals โ†’ Align decimal points


๐ŸŒŸ Real-life Examples

Temperature changes ๐ŸŒก๏ธ

  • -3ยฐC + 7ยฐC = 4ยฐC

Money profit & loss ๐Ÿ’ฐ

  • โ‚น500 – โ‚น800 = -โ‚น300

Learn with an example

๐ŸŽฏ Add. 3 1/2 + -1/2 = _________

  • You are adding two numbers with different signs, so subtract the lesser absolute value from the greater absolute value:
  • 3 1/2 – 1/2 = 3
  • Since the number with the greater absolute value is positive, the result must also be positive.
  • So: 3 1/2 + – 1/2 = 3

๐Ÿ‘‰ Add. -4 + 1/2 = _____

  • You are adding two numbers with different signs, so subtract the lesser absolute value from the greater absolute value:
  • 4 – 1/2
  • 3 1/2
  • Since the number with the greater absolute value is negative, the result must also be negative:
  • 3 1/2 —-> – 3 1/2
  • So: – 4 + 1/2 = -3 1/2

๐ŸŽฏ Add. – 8 + 9 / 10 ____

  • You are adding two numbers with different signs, so subtract the lesser absolute value from the greater absolute value:
  • 8 – 9/10 = 7 1/10
  • Since the number with the greater absolute value is negative, the result must also be negative:
  • 7 1/10 —-> – 7 1/10
  • So: – 8 + 9/10 = – 7 1/10

Let’s practice!๐Ÿ–Š๏ธ