Common Mistakes in GATE NAT Questions
In a GATE numerical answer type (NAT) question there are no options: you type a number using an on-screen keypad, and you work it out with the on-screen virtual calculator, the only calculator allowed. NAT questions carry no negative marking, so a wrong answer costs nothing beyond the marks you don't get. That makes the mistakes below doubly painful: they usually come from knowing the method and slipping on the number.
Mistake 1: degrees and radians
sin 30 is 0.5 only in degrees. In radians, sin(30) = −0.988. If a question gives an angle in degrees, check which mode the calculator is in before you trust the result. A sanity check catches it: an angle of 30 degrees can't have a negative sine.
Mistake 2: log base
Semiconductor and transient formulas use the natural log. The voltage for a tenfold rise in diode current is ηVT ln 10 = 0.02585 × 2.303 ≈ 59.5 mV for η = 1. Use log10(10) = 1 by mistake and you get 25.85 mV, less than half the right answer.
Mistake 3: rounding too early
A capacitor charging towards 10 V has v = 10(1 − e^(−0.7)) after 0.7 time constants. Done properly, that's 5.034 V. Round e^(−0.7) to 0.5 halfway through and you get 5.000 V. If the question asks for two decimal places, that's 5.03 against 5.00: a lost answer from a correct method. Keep full precision until the last step, then round once, the way the question asks.
Mistake 4: the unit asked for
The energy in a 4.7 µF capacitor at 12 V is ½CV² = 0.5 × 4.7 × 10⁻⁶ × 144 = 3.384 × 10⁻⁴ J. If the question asks for millijoules, the answer is 0.3384, not 338.4 (that's microjoules) and not 0.0003384 (joules). Read the unit in the question last, just before you type.
Mistake 5: dropping a sign
When a question defines a direction or polarity, a negative answer can be correct. In a circuit where a branch current comes out as −6 A against the direction the question drew, the answer is −6, not 6. Don't tidy away a minus sign unless the question asks for a magnitude.
A 20-second check before you submit
- Is the calculator in the right angle mode?
- Did I use ln or log10 as the formula needs?
- Did I round only at the end, as the question asks?
- Is the number in the unit the question asks for?
- Does the sign match the direction the question defined?
- Is the size plausible?
Always answer
Because NAT questions carry no negative marking, a reasoned estimate is always worth typing in when you're short of time. That's different from MCQs, where a wrong answer costs a third or two-thirds of the question's marks.
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Sources and last verified date
Every GATE 2027 fact in this post was checked against the official GATE 2027 website, information brochure and syllabus PDFs from IIT Madras on 7 October 2026. Official dates and rules can change, so confirm anything you plan around on the official site.