Add and subtract rational numbers
Key notes:
๐ข What Are Rational Numbers?
- Rational numbers are numbers that can be written as a fraction ๐ฅง
- Example: 1/2, -3/4, 5, -8, 0.25 ( = 1/4 )
- They include positive, negative, fractions, and decimals! ๐
โ Adding Rational Numbers with the Same Sign
Add normally and keep the same sign โ๏ธ
Example:
- 3/5 + 2/5 = 5/5 = 1 ๐
- -4 + -2 = -6
๐ก Same side = team up! ๐ค
๐ 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
๐ก Opposites try to cancel each other! โกโก
โ Subtracting Rational Numbers
Change subtraction to addition of the opposite โจ
Example:
- 4 – 7 = 4 + (-7) = -3
- -3 – 5 = -3 + (-5) = -8
๐ก Subtracting becomes adding the opposite! ๐
๐ฐ Adding & Subtracting Fractions
๐ If denominators are the same:
Add/subtract numerators only!
- 3/8 + 2/8 = 5/8
- 7/9 – 4/9 = 3/9 = 1/3
๐ If denominators are different:
Find LCM (Least Common Multiple) ๐ฏ
Convert to equivalent fractions
Add/subtract numerators
- 1/4 + 1/6 โ LCM = 12
- 3/12 + 2/12 = 5/12
๐ง Adding & Subtracting Decimals
Line up the decimal points
Add or subtract normally
- 3.75 + 2.1 = 5.85
- 6.4 – 3.25 = 3.15
๐๏ธ Keep decimals in the right place! ๐
๐ฏ Opposites and Zero Pair
A number and its opposite always add to 0
- 5 + (-5) = 0
- -8 + 8 = 0
๐ฅ They cancel each other! ๐ซ
๐งฎ Key Rule to Remember
โ๏ธ Addition โ Follow sign rules
โ๏ธ Subtraction โ Add the opposite
โ๏ธ Fractions โ Use LCM
โ๏ธ Decimals โ Align decimal points
๐ Real-life Examples
Temperature changes ๐ก๏ธ
- -3ยฐC + 7ยฐC = 4ยฐC
Money profit & loss ๐ฐ
- โน500 – โน800 = -โน300
Learn with an example
๐ฏ 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
๐ 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
๐ฏ 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!๐๏ธ

