Use a blue/black ballpoint pen, shade one full bubble per question from the outer edge inward, check your question alignment every 10 rows, and never erase or use correction fluid. Reserve the last five minutes to scan the sheet in straight rows, then columns.
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Why the OMR decides more marks than you think Pen selection: gel vs smooth ballpoint The "bubble-first" shading rule The alignment trap No erasing, no correction fluid Your last-5-minutes OMR routine Frequently asked questionsWhy the OMR Decides More Marks Than You Think
The exam is 100 MCQs in 2 hours, scanned by an Optical Mark Reader. The scanner only sees dark, fully-shaded bubbles in the correct position. It does not see your rough work, it does not see what you “meant”, and it cannot read a half-shaded mark.
That makes OMR skill worth real marks. A student who knows 80 answers but mis-marks 5 of them scores the same as a student who only knew 75. On a merit list where 35 is the pass line and every mark moves your rank, this is not a small detail — it is the difference between two colleges.
Pen Selection: Gel vs Smooth Ballpoint
What pen you carry matters more than most people think. TU IOST's own OMR guide specifies a blue or black ballpoint pen, and there is a reason for that.
- Gel pens lay down ink that dries more slowly. When you shade bubble after bubble in a row, your hand can drag wet ink and smear it across a neighbouring bubble. The scanner reads any dark, clean mark — gel included — so this is a practical preference for ballpoint, not a ban on gel pens.
- Ballpoint ink dries instantly, sits flat and shades evenly. It is the safe choice for a fast-shading OMR session.
- Pencil is a no. It is erasable, but OMR scanners are tuned for pen — a light pencil mark may not register at all.
Take a spare ballpoint. A dead pen halfway through the exam is an emergency you do not want on exam day.
The "Bubble-First" Shading Rule
How you shade matters as much as what you shade. The official rule is simple — darken the complete circle. The practical technique is the bubble-first rule: fill from the outer edge of the circle inward, in one direction, so the whole bubble gets covered without scribbling outside it.
- Start at the edge of the circle and work your way inside, filling completely in one pass.
- Do not scribble wildly — random dots outside the bubble can be read as a stray mark and invalidate the answer.
- Do not half-shade. There is no official percentage threshold — the safe advice is simply to darken the bubble completely so the scanner reads one clean mark.
The Alignment Trap
This is the most expensive mistake in the exam because it compounds. If you misalign by one question early — you skip Q25 but bubble your Q25 answer into Q24's row — every answer after it shifts by one. A student who loses 30 questions that way did not make 30 mistakes; they made one.
The fix is a rhythm, not extra effort:
- Bubble in small batches. Solve 5 questions, bubble 5, then move on. Never solve twenty questions and bubble them all from memory.
- Check alignment every 10 questions. Confirm the question number on the paper matches the row you are filling. Ten seconds of checking every ten questions costs two minutes total — a misaligned OMR costs an entire section.
- When you skip a question using the 45-second rule from the tips & tricks guide, leave its bubble blank and mark the skip on the question paper so Pass 3 brings you back to the right number.
No Erasing, No Correction Fluid
Here is the rule that saves the most careless students: once a bubble is marked, do not fight it.
- Erasers leave smudges that scanners can read as a stray mark.
- Correction fluid or tape lifts the paper and can make the sheet unreadable — or rejected outright.
- The act of “fixing” is where double-marks happen. Two bubbles on one question invalidates it completely, even if the second bubble is the correct answer.
If you have already bubbled an answer and later realise it is wrong, your best move is almost always to leave it and move forward. Correction methods are prohibited, and the risk of invalidating the question is higher than the value of fixing one mark — and dwelling on it will cost you the next ten questions. The one exception: if the invigilator hands you a replacement sheet due to a printing defect or before the OMR is officially accepted, follow their instructions instead.
Your Last-5-Minutes OMR Routine
In the final five minutes, stop solving. The marks you bank now are worth more than any question you might still crack:
- Scan in straight rows — left to right — and confirm every row has exactly one bubble.
- Scan in straight columns — top to bottom — to catch a skipped row, the classic misalignment tell.
- Fill any remaining blanks with your best guess. There is no negative marking — a guess is free, a blank is a gift to the person below you on the merit list.
- Leave the sheet flat and clean. No folding, no crumpling, no doodling near the bubbles.