Arithmetic: slow speed and silly mistakes have the same cause

Two of the most frequent Quant doubts we get, and both have answers that sound unglamorous. One is about foundations that are not automatic yet. The other is about the difference between watching a solution and producing one.

Arithmetic does not work, mistakes happen, and I am slow

Arithmetic doesn’t work at all, silly mistakes happen, and speed is very slow.

Arithmetic bilkul nahi banti, silly mistakes ho jaati hain, aur speed bhi bahut slow hai.

Slow speed and silly mistakes almost always come from the same root cause: the basic building blocks are not automatic yet, so the brain is doing real calculation work on things that should be instant recall.

That mental load is exactly where silly mistakes creep in. A carried digit forgotten. A percentage misread as a fraction. Not because the concept was wrong, but because attention was split between the easy part and the hard part of the same question.

So fix the foundation before touching speed:

• Tables to 30
• Squares to 50
• Cubes to 20
• Common percentage-to-fraction conversions

Not “revised” — memorised, until they take zero thinking.

Then run a focused daily slot of fifteen to twenty pure arithmetic questions under a timer. And when a mistake happens, note exactly which step it was in:

1. Misread the question
2. Wrong operation chosen
3. Calculation slip

That pattern usually repeats, and it is fixable once it is named.

Speed comes after this, not before it. Trying to go fast on shaky basics is precisely what produces both problems at once — which is why “practise faster” tends to make the accuracy worse rather than the speed better.

I understand the lecture and then cannot solve anything

Arithmetic feels understood while watching lectures, but when it comes to solving independently, questions don’t build — leading to demotivation. Also, quant videos eat up a lot of time without corresponding question-solving output.

Lectures ke samay saare samajh aate hain, attempt karne jao to nahi hote — demotivation aa jata hai. Video dekhne mein hi time nikal jaata hai, questions bante nahi.

This gap between watching and solving is one of the most common and most misleading experiences in Quant preparation — and it is worth understanding why it misleads, because that is what makes the fix believable.

Watching someone else solve a question genuinely does feel like understanding. Your brain is following a path that someone else already built, and following a path is easy. Independent solving requires building the path yourself, which is an entirely different cognitive task. It develops through active struggle, not through more watching.

The concrete fix is a hard ratio shift:

For every one hour of video, at least two hours of solving — without pausing to look anything up.

Even if you get stuck and produce nothing for five to ten minutes on a single question, that stuck time is exactly where the real learning happens. More than the video did. This is the part that feels like failure and is not.

And if a topic keeps producing zero independent output no matter how many videos you watch on it, that is the signal to stop watching more content on it. Instead, solve fifteen to twenty basic-level questions on just that topic, checking the solution only after you have genuinely attempted each one.

On the demotivation

It is worth naming directly, because the reader did. The demotivation in this doubt is not a character flaw and it is not evidence that you are bad at Quant. It is the predictable result of a routine where the input feels productive and the output stays at zero.

Change the ratio and the output changes, usually within a couple of weeks. The motivation tends to follow the output rather than the other way round.