GuideMath · P5 / P6Problem Sums
Before-After Problem Sums Guide
In before-after problems, one quantity changes while another may stay constant. Draw two bar models: one for BEFORE, one for AFTER.
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1
Read Twice
Underline what changed. Circle what stayed the same.
2
Draw Two Bars
One bar for BEFORE, one for AFTER. Line them up.
3
Find the Constant
Total, difference, or one quantity often stays the same. Use it to find 1 unit.
⚠️ Common Mistakes
Don't fall into these traps
- ✕Drawing only one model
- ✕Missing which quantity is constant
- ✕Adding units across before and after without checking
Teacher Hidayah's Tip
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Label BEFORE and AFTER above your bars. Always.
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Sample Question
Try it, then read the worked solution
Question
Ali had twice as much money as Ben. After Ali spent $20, they had equal amounts. How much did Ben have?
Worked Solution
- 1Before: Ali = 2 units, Ben = 1 unit
- 2After spending $20, Ali = Ben → 2 units − $20 = 1 unit
- 31 unit = $20 → Ben = $20
Everything for Problem Sums
Each topic in the library comes with the full 5-piece bundle.
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Before-Class Prep
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After-Class Practice
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Downloadable Notes
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One-Page Mind Map
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Mistake Fix Zone