Common Exam Traps

Under the 90-second clock, students square both sides of $\sqrt{f(x)} = g(x)$ or cross-multiply $\frac{A(x)}{B(x)} > C$ without recording the domain restriction $B(x) eq 0$ or $g(x) \ge 0$ on Line 1. In sequences and trig intervals $[0, 2\pi]$, students count $b - a$ instead of $b - a + 1$ boundary solutions.

When rebounds, decelerations, or potential differences are treated as scalars rather than signed vectors, $\Delta p = m(v - (-u)) = m(v + u)$ collapses into $m(v - u)$. Similarly, dividing an inequality by $\ln(0.5) < 0$ without flipping $>$ to $<$ hands the mark directly to the examiner’s twin distractor.

Examiners love giving capillary bore diameter $d$ instead of radius $r$ (introducing a factor of $2^2 = 4$ error in $\pi r^2$), diatomic gases $\text{O}_2 / \text{Cl}_2$ (factor of $2$ in atom counts), and diprotic $\text{H}_2\text{SO}_4 + 2\text{NaOH}$ titrations where students equate $C_1 V_1 = C_2 V_2$ without the $1:2$ stoichiometric coefficient.

After 60 seconds of intense mental algebra, solving $x = 4$ triggers a dopamine hit—and the examiner places $4$ right at Option A. In reality, the final sentence of the stem asked for the area $x^2 = 16$, the complement probability $1 - p$, or the remaining unreacted volume.

Evaluating statements 1, 2, 3, and 4 sequentially from top to bottom wastes 90+ seconds because Statement 1 is often the hardest algebra derivation while Statement 3 is a 4-second conceptual myth that eliminates 3 of the 5 options immediately.

Writing $T - m_1 g = m_1 a$ and $m_2 g - T = m_2 a$ separately takes 110 seconds and often drops a sign on internal tension $T$. Similarly, averaging two densities $\frac{\rho_1 + \rho_2}{2}$ or two speeds $\frac{v_1 + v_2}{2}$ ignores the total-system conservation law.

Because $1\text{ m} = 10^2\text{ cm}$, students reflexively divide area in $\text{cm}^2$ by $10^2$ instead of $(10^2)^2 = 10^4$, or volume in $\text{mm}^3$ by $10^3$ instead of $(10^3)^3 = 10^9$. Examiners populate options A–E with identical mantissas across four different powers of 10.

When presented with a 4-column, 6-row table (Options A–F), students instinctively read Row A across all 4 columns, then Row B across all 4 columns—performing 24 cell evaluations. Yet one column is always a binary check (e.g., "Anode Sign" or "Mitosis vs Meiosis") that eliminates 50%–67% of rows in 4 seconds.