1. Answering the question you expected, not the one asked
The most expensive error on the paper. "Which is not a property of..." is read as "which is", and a candidate who knows the topic perfectly gets it wrong. JAMB uses negative phrasing, "except", and "least likely" deliberately.
The fix is mechanical: find the operative word in every question before looking at the options. On screen you cannot underline, so say it in your head. It costs two seconds and it protects several marks per paper.
2. Running out of time in the last subject
One clock covers four subjects, so overspending early is borrowed directly from the end. The classic shape is a candidate who does beautifully in their first two subjects and guesses wildly through the fourth.
Decide a rough time budget per subject before you start, and check yourself against it at the quarter marks. If you are behind, do not try to make it up by rushing the current subject — move on and come back.
3. Leaving questions blank
There is no penalty for a wrong answer. A blank is a guaranteed zero, a guess is not, so a blank is strictly worse. Yet every year candidates run out of time with unanswered questions still on the grid.
Use the last two minutes of each subject to fill every remaining blank with something. Not carefully — just fill them.
4. Changing correct answers
Second-guessing under stress usually makes things worse. Change an answer when you have a concrete reason — you misread it, you spotted an error in your working, you remembered the rule. Do not change one because it "feels wrong" on a second look. That feeling is anxiety, not insight.
5. Getting stuck out of pride
A question you nearly have is the most dangerous item on the paper. It pulls minutes out of you because sunk effort makes quitting feel wasteful. Set a hard rule: if it is not moving in about a minute, mark it and go. You can come back, and you will come back with a clearer head and more marks already banked.
How to actually train these out
None of these are knowledge problems, so more reading will not touch them. They only appear under time pressure, which means timed mocks are the only place you can find and fix them. After every mock, count how many marks you lost to execution rather than to ignorance. For most candidates the number is uncomfortable — and it is the fastest score improvement available, because you already know the material.
Questions people ask
What is the most expensive careless mistake in JAMB?
Answering the question you expected instead of the one asked. JAMB uses negative phrasing, except, and least likely deliberately. Find the operative word in every question before you look at the options.
Should I ever leave a JAMB question blank?
No. There is no penalty for a wrong answer, so a blank is a guaranteed zero and a guess is not. Use the last two minutes of each subject to fill every remaining blank with something.
Should I change an answer if I have second thoughts?
Only when you have a concrete reason: you misread it, you spotted an error in your working, or you remembered the rule. Do not change one because it feels wrong on a second look. That feeling is anxiety, not insight.
How do I train careless mistakes out?
None of them are knowledge problems, so more reading will not touch them. They only appear under time pressure, so timed mocks are the only place to find and fix them. After each mock, count how many marks you lost to execution rather than to ignorance.
Practise this, don't just read it. Execution errors only show up under time pressure, which is the only place you can train them away. JAMBUDDY gives you timed mocks and 20,000+ real past questions inside Telegram, free for 14 days. Open @jamb_buddy_bot.