Class 5 · Topic 16
Commercial Maths & Proportion
Step 1 · Learn
Read the ideas
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Percentage
Fraction × 100 = percentage. % ÷ 100 = fraction.
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Unitary Method
Divide for one, multiply for many.
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Percentage of a Quantity
Convert % to fraction, then multiply.
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Ratio & Proportion
Simplify by hcf. Cross-multiply to check proportions.
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Speed, Distance & Time
Triangle trick: cover the unknown, read the formula.
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Simple Interest
si = (P × R × T) ÷ 100. Per year.
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Counting Principle
M ways × N ways = M × N total combos. Always multiply, never add.
Step 2 · Practice
Try the quests
Step 3 · Boss Battle
Beat the boss
🛡️ 🛡️ 🛡️ 3 shields — lose all → 60-second cooldown
Round 1
The Mint ranks four trainees by accuracy: A…
🔒Round 2
A shop sells 8 notebooks for 96 rupees. A…
🔒Round 3
After a 20 percent discount, a bag sells…
🔒Round 4
The vault holds 4,200 rupees, shared among…
🔒Round 5
A courier covers 45 km in 1 hour 30…
🔒Round 6
A deposit earns simple interest at 5…
🔒Round 7
The final lock needs a 3-letter code chosen…
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