Everyday Maths: percentages, prices and estimates
The maths that comes up in daily life: a percent of a number, discounts, GST and tips, percentage change, squares up to 30 and cubes up to 15, and quick estimates. Each level starts with a short lesson on the method.
The levels
Percentages and prices
- 1.1 Percent of a number
- 1.2 Discounts
- 1.3 GST and tips
- 1.4 Percentage change
Number sense
- 2.1 Squares to 30
- 2.2 Cubes to 15
- 2.3 Estimate
- 2.4 Everyday Boss
The lessons
Before its first questions, each of these levels shows a short lesson: an example to try, the method, and why it works.
1.1 Percent of a number
10% of a number is the number ÷ 10; 1% is ÷ 100. Build other percents from those: 25% of 640 is a quarter, 160; 15% is 10% + 5% (64 + 32 = 96).
Why it works: Percent means "out of 100", so 25% of 640 is 640 × 25 ÷ 100. Splitting into easy parts is quicker in your head.
1.2 Discounts
Work out the discount, then take it away: 25% off ₹480 is 480 − 120 = ₹360. Or pay the rest straight away: 25% off means you pay 75%.
Why it works: Both ways give the same price; use whichever percent is easier.
1.3 GST and tips
Add the tax to the price: ₹600 with 18% GST is 600 + 108 = ₹708. For 18%, take 10% (60) + 8% (48).
Why it works: Since 22 September 2025, India's main GST rates are 5% and 18%, with 40% on a few luxury and 'sin' goods. A tip works the same way: 10% of ₹600 adds ₹60.
1.4 Percentage change
Percentage change = change ÷ the old price × 100. From ₹80 to ₹100 is a change of 20, and 20 ÷ 80 = 25%.
Why it works: Always divide by where you started: from ₹100 down to ₹80 is a 20% drop, not 25%.
2.1 Squares to 30
For numbers near a round one, go up and down: 23² = 20 × 26 + 3² = 520 + 9 = 529. Squares ending in 5: 25² is 2 × 3 = 6, then 25: 625.
Why it works: (a − b)(a + b) = a² − b², so a² = (a − b)(a + b) + b². Knowing squares to 30 speeds up exam sums a lot.
2.2 Cubes to 15
A cube is the number times itself, three times: 12³ = 12 × 12 × 12 = 144 × 12 = 1,728. Learn 1³ to 10³ by heart (1, 8, 27, 64, 125, 216, 343, 512, 729, 1000).
Why it works: Cubes come up in volumes and in exam simplification questions.
2.3 Estimate
Round each number to an easy one, then multiply: 49.8 × 20.1 is about 50 × 20 = 1,000. Answers within 5% count.
Why it works: Estimating first catches big mistakes, and it's often all you need (bills, shopping).
More games
- Maths: Addition to long division, in your head.
- Reasoning: Patterns, logic puzzles and thinking traps.
- Memory: Chunking, the memory palace and the major system.
- General Knowledge: Nature, geography, science, history and more.
- Speed Tricks: Tricks like ×11 and squares ending in 5.
- Map quiz: Countries, capitals, rivers and peaks on the map.