Math · Stage 5

Solve harder assumption, excess-deficit and before-after problems

Three olympiad power-moves on one page: PRETEND everything is the same kind (assumption), compare two sharing plans to find how many people (excess-and-deficit), and anchor on what never changes (before-after).

✦ Math📘 Stage 5 · S5⏱ ~15 min🧒 Ages 9–10★ Free to start

I can solve harder assumption, excess-deficit and before-after problems.

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Kavi the Problem Whisperer 🕵️

A page of word problems lands on Kavi's branch — no bar models, just clever reasoning! "I know three tricks for these," hoots Kavi. "Pretend everything is the same kind and fix the gap. Compare two plans — what's left over and what's short tells me how many people. And for before-and-after, I hunt for the one thing that never changes. Watch me crack all three! 🕵️"

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What your child will learn

1Pretend they are all the same, then fix the gap

2Real total − pretend total = the gapHere are 12 vehicles with 38 wheels (bikes have 2 wheels, cars have 4). Pretend every one is a bike: 12 × 2 = 24 wheels. The gap is the real 38 take away the pretend 24. Tap Step → to build 38 − 24.

3Two sharing plans tell you how many people

4Hunt for the thing that NEVER changesIn a before-after story something is secretly fixed. Find it and the puzzle falls apart. Tap each card.

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A peek inside

A test has 20 questions. Each right answer scores +4, each wrong answer −1. Mira answered every question and scored 35. How many did she get right?

assumption: pretend all right → 20 × 4 = 80 · too many by 80 − 35 = 45 · each wrong costs 4 + 1 = 5 → wrong 45 ÷ 5 = 9 · right 20 − 9 = 11

Try this at home: Assumption: 15 coins are 10¢ and 50¢, worth 350¢ in all. Pretend all 10¢ → 150¢; the extra is 350 − 150 = 200; each 50¢ adds 40¢, so 50¢ coins = 200 ÷ 40 = __

Ready to play and learn?

Start the free interactive lesson, or print the handout for screen-free play.

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Part of Math · Stage 5 · S5 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.