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Everyday maths

Percentages, discounts, change, splitting a bill, clock times, speed, price per gram, exchange rates and interest — the arithmetic of an ordinary day.

  • Number sense
  • Timed
  • Endless levels

How it plays

Each question is a situation from an ordinary day: a discount on a price, the change from a note, a bill split four ways, a train that leaves at 10:45 and takes 2 h 35 min.

New kinds of question unlock as you climb, and the numbers start round and get awkward — 25% of 400 is easy; 18% of 1,365 is the real skill. Every answer comes with the working.

Some questions are traps on purpose: up 10% then down 10% is not back where you started.

Keys

Space starts and skips ahead · 1–9 pick · Enter submits · Esc stops. On a phone, tap.

What it trains

This practises the specific calculations of daily life, and practising them makes them quicker. It claims nothing beyond that.

Learn

How to get better at everyday maths: the method, the techniques, what each new level asks of you, and the traps the wrong answers are made of.

Your approach to each question

  1. Read what is asked before the numbers: the discount or the price you pay, the change or the cost, the time it is then or how long it took.
  2. Say the size before you calculate: 12% of 3,950 is “a bit more than 10%, so a bit over 395”. That one sentence rules out every slip of ten.
  3. Break the number into easy parts — 10%, 5%, 1%; whole hours, then minutes; to the next ten, then the next hundred — and add the parts as you go.
  4. Check the answer against the question’s own sense: change is less than the note, a discounted price is less than the price, a speed in km/h is distance per hour.

Techniques and tricks

  • Build any per cent from 10% and 1%

    10% is a shift of the decimal point; 5% is half of that; 1% is a shift of two places. Every other per cent is a sum or a difference of these.

    e.g. 15% of 1,180 = 118 + 59 = 177; 12% of 3,950 = 395 + 79 = 474

  • Pay the rest, not the discount

    Work the discount, then take it off — or go straight to the part you pay: 7% off means you pay 93%.

    e.g. ₹4,600, 7% off: 1% is 46, so 7% is 322, and you pay ₹4,600 − ₹322 = ₹4,278

  • Count up for change

    Shop-keeper’s subtraction: from the cost, step up to the next ten, then the next hundred, then the note, and add the steps.

    e.g. ₹347 paid with ₹500: 3 to 350, 50 to 400, 100 to 500 — ₹153

  • Clock times in two moves

    Add or count the whole hours first, then the minutes, and cross the hour at 60, never at 100. For a gap, go to the next whole hour, then whole hours, then the rest.

    e.g. 10:45 to 13:20: 15 min to 11:00, 2 h to 13:00, 20 min more — 2 h 35 min

  • Change over where you started

    A percentage change is the difference divided by the starting value. The end value is never the base.

    e.g. From 800 to 920: 120 ÷ 800 = +15%

  • Changes multiply

    Successive percentage changes multiply as factors. As a shortcut, a% then b% is a + b + (a × b ÷ 100), with falls counted as negative.

    e.g. Up 20%, then down 25%: 1.2 × 0.75 = 0.9, so −10%. Or 20 − 25 + (20 × −25 ÷ 100) = −10.

  • Price per 100 g

    Bring both packs to the same weight, usually 100 g, before comparing. Divide each price by its weight in hundreds of grams.

    e.g. A: 250 g for ₹60 is ₹24 per 100 g. B: 400 g for ₹92 is ₹23 per 100 g. B is cheaper.

As the levels climb

  • New kinds of question unlock in the order they are listed under “Kinds of question”: per cents and discounts first, then change, bills, clock times, speed, price per unit, percentage change, exchange rates, simple interest and, last, successive changes. Each newcomer is asked about more often while it is new.
  • The numbers start in round hundreds, then fifties, tens, fives, and then anything — and after that they keep growing in size. The per cents follow: 10, 25 and 50 at first, then awkward ones like 7, 12, 18 and 45. That is when building from 10% and 1% pays off.
  • Clock questions gain odd minutes as they climb: first whole hours, then halves and quarters, then any number of minutes. Write the time to the next hour down first; it is where most slips happen.
  • The clock for each question shrinks to 55% of its starting time. With awkward numbers there is only time for one decomposition, so pick the parts before you start adding.

Traps to avoid

  • A slip of ten: 15% of 1,180 answered as 1,770 or 17.7. Check the size first — 10% of 1,180 is 118, so 15% must be a bit more than that.
  • The discount given instead of the price, or taken off twice: ₹322 or ₹3,956 instead of ₹4,278 for 7% off ₹4,600. Read again whether the question asks what you save or what you pay.
  • Minutes counted in hundreds. Borrowing 100 instead of 60 makes an answer 40 minutes out, which is why answers 40 minutes out are so often among the options.
  • Up 10% then down 10% taken as no change, or a change divided by the end value. Factors multiply; the base is where you started.
  • Exchange done the wrong way round: dividing by the rate instead of multiplying. If 1 $ = ₹84, then 45 $ must be many more rupees than 45.

How to practise

  • Use “Kinds of question” to drill one kind on its own — “Clock: how long between” or “Successive changes” — when it is the one you miss. Tick the others back on afterwards and they unlock again in order.
  • Set “Currency” to the one you shop in, so the amounts feel like real prices.
  • Switch “Answer by” to “Typing the number, where it is a number” once options feel easy. Clock and price-per-unit questions stay as choices; the rest must be produced, not recognised.
  • Keep “Options shown” at 4 at first. Raise it to 6 to make the size check do more work, since more of the options will be near the right size.

Levels

Each question has a clock that comes from the work it asks for. There is no last level: at least one dial turns without end. Your level is judged on your last ten answers, every ten: 90% moves you up, below 80% moves you down, which holds most people near four in five right.

All of it is in the settings beside Start — how many answers a judgement looks at and how often it recalibrates, the thresholds, the time, which questions, how many options, and whether you see each verdict at once or review them together at the judgement. You can also jump to any level.

More number sense

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