GuideMath · P5 / P6Problem Sums
Before-After Problem Sums Guide
Track what changed and what stayed the same.
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Bar model
Draw the parts, then the whole.
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
- Drawing only one model
- Missing which quantity is constant
- Adding units across before and after without checking
Teaching Team Tip
Label BEFORE and AFTER above your bars. Always.
Worked Example
Try it, then check the steps
Question
Ali had twice as much money as Ben. After Ali spent $20, they had equal amounts. How much did Ben have?
Steps
- 1Before: Ali = 2 units, Ben = 1 unit
- 2After spending $20, Ali = Ben → 2 units − $20 = 1 unit
- 31 unit = $20 → Ben = $20
What to do next
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