MathematicsChapter 5: Algebraic Fractions
Number Lcds
x/2 + x/5 = 7x/10. LCD 10.
Learning objectives
- Define and explain number lcds.
- Apply number lcds to a focused FBISE question.
- Check the answer for correct terms, evidence, working, and units.
Definition
x/2 + x/5 = 7x/10. LCD 10. x-22 + x+109 uses LCD 18: 9(x-2)+2(x+10) all over 18 = 11x+1618.
Where / symbols
- Number Lcds
- x/2 + x/5 = 7x/10. LCD 10. (x-2)/2 + (x+10)/9 uses LCD 18: 9(x-2)+2(x+10) all over 18 = (11x+16)/18.
Overview
Learn the idea, then use it:
Core Understanding
x/2 + x/5 = 7x/10. LCD 10. x-22 + x+109 uses LCD 18: 9(x-2)+2(x+10) all over 18 = 11x+1618.
Examples LCM of bottoms · LCD from factors · then combine tops · NUMBER LCDS: x/2 + x/5 = 7x/10. LCD 10. (x-2)/2 + (x+10)/9 uses LCD 18: 9(x-2)+2(x+10) all over 18 = (11x+16)/18.
Exam Application
State the correct term, connect it to the chapter rule or evidence, and use a clear example or calculation.
Examples Define first · Show the rule or evidence · Check units, labels, and conclusion
WHAT — NUMBER LCDS
x/2 + x/5 = 7x/10. LCD 10. x-22 + x+109 uses LCD 18: 9(x-2)+2(x+10) all over 18 = 11x+1618.
HOW — Use the idea
Identify what is given, select this topic's rule or evidence, apply it one step at a time, and check the result.
In simple words
Do not merge number lcds with a neighbouring idea that uses a different definition, rule, or method.
Key points
- LCM of bottoms
- LCD from factors
- then combine tops
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Number Lcds
Sticky Notes · Quick Revision
Core Idea
- x/2 + x/5 = 7x/10.
Key Points
- LCM of bottoms
- LCD from factors
- then combine tops
Simple Check
- Explain number lcds in your own words and connect it to one chapter example.
How to Answer
- Define the idea, show the main rule or evidence, apply it, and check the final statement.
Common Mistake
- Do not merge number lcds with a neighbouring idea that uses a different definition, rule, or method.
FBISE Exam Tip
- Use the exact term, show working where needed, and include units or labelled evidence.
60-second revision
- x/2 + x/5 = 7x/10.
- LCM of bottoms
- LCD from factors
- then combine tops
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