Running total
Numbers flash one at a time — keep the running total in your head and give it at the end. More numbers, bigger, faster, then minus signs.
How it plays
Each number is shown for a moment and taken away; add it to what you are holding before the next one arrives. When they stop, give the total.
Levels add a number, raise the size, shorten the time each is shown, and bring in subtraction — first one minus hidden among the pluses, then both mixed freely. Count and size never stop growing.
The wrong options are the real slips: the last number missed, a minus read as a plus, a ten carried wrong. The working shows the total after every step.
Keys
Space starts and skips ahead · 1–9 pick · Enter submits · Esc stops. On a phone, tap.
What it trains
This trains keeping and updating a sum in mind as numbers arrive. It is practice at running totals, not a measured gain in memory or intelligence elsewhere.
Learn
How to get better at running total: 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
- Take the first number as your total. Nothing else needs remembering from then on.
- On each new flash, read the sign before the number. A minus read as a plus is the costliest slip there is.
- Fold the number into your total at once and say the new total to yourself, once. Then let the flash go; you will never need it again.
- When the flashes stop, the total you are holding is the answer. Give it straight away: the answer time is about 4 seconds plus a little for each digit.
Techniques and tricks
Biggest part first
Add or take the tens first, then the units. The total stays roughly right even if you are rushed at the end.
e.g. Total 47, + 26: 47 + 20 = 67, + 6 = 73.
Round and compensate
Treat 19 as 20 − 1, 28 as 30 − 2: add the round number, then correct.
e.g. Total 54, + 19: 54 + 20 = 74, − 1 = 73.
Take away the next ten
For a minus, take away the round number just above it, then give back the difference.
e.g. Total 63, − 18: 63 − 20 = 43, + 2 = 45.
Make tens
When the units of the total and the new number make 10, the units drop to 0 and the tens go up by one more.
e.g. Total 37, + 13: 7 and 3 make ten, so 50.
One word for the total
Hold the total as a single spoken number, “seventy-three”, not as digits. One word survives the next flash better than a string of them.
As the levels climb
- Four things take turns: one more number, bigger numbers, a shorter flash and the signs. Count and size never stop growing.
- Numbers grow by about 30% a notch: up to 9, then 12, 15, 20, 26 and on. Past 20, switch from counting on to adding tens then units.
- Each flash shortens from 1,500 ms through 1,300, 1,120, 980, 860, 760 and 680 to 620 ms. The gap between flashes stays the same, so learn to add while the number is still showing.
- The signs change twice: one minus hidden among the pluses from level 4, then plus and minus mixed freely from level 8. The total never goes below zero, so a minus is never bigger than what you hold.
Traps to avoid
- The last number missed. Your total is short by exactly the final flash. It happens when you relax before the run ends; keep counting until the “Total?” prompt appears.
- A number in the middle missed. You were still adding the one before when it came. Glance at the new flash first, then finish the sum.
- A minus read as a plus. The total comes out too big by twice that number. Read the sign first, every time, once minus signs have started.
- Ten out or one out, from a carry in the head. Check the units of your total as you go: they depend only on the units of the numbers.
How to practise
- Use the Signs setting to practise one schedule: “+ only” to build speed, “one − among the +” to train reading the sign, “+ and − mixed” for the full skill.
- Raise “Numbers at level 0” to start longer runs straight away once short ones are easy; keeping going is a skill of its own.
- Switch Answer by to “Typing the number”. Options show the missed-number totals beside the right one, which helps you check rather than hold.
- When you miss, read the “Running” line in the working: it shows the total after each flash, so you can see exactly where yours went off.
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 calculation
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