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If the matrix $P = \begin{pmatrix}1 & \alpha & 3\\1 & 3 & 3\\2 & 4 & 4\end{pmatrix}$ is the adjoint of a $3\times3$ matrix $A$ with $|A|=4$, find $\alpha$.
We use the property: $|adj(A)| = |A|^{n-1}$ for an $n\times n$ matrix. Here $n=3$, so $|P| = |A|^2 = 16$.
Compute $|P|$ by expanding along row 1 (with unknown $\alpha$):
$|P| = 1(3\cdot4-3\cdot4) - \alpha(1\cdot4-3\cdot2) + 3(1\cdot4-3\cdot2)$
$= 1(0) - \alpha(4-6) + 3(4-6) = 2\alpha - 6$
Setting $2\alpha - 6 = 16 \Rightarrow 2\alpha = 22 \Rightarrow \alpha = \mathbf{11}$
The base triangle has sides 5, 12, 13 — this is a right triangle (since \(5^2 + 12^2 = 25 + 144 = 169 = 13^2\).
Base area = \(\dfrac{1}{2} \times 5 \times 12 = 30\ \text{cm}^2\
Perimeter of base = \(5 + 12 + 13 = 30\ \text{cm}\
Lateral surface area = Perimeter × Height = \(30 \times 10 = 300\ \text{cm}^2\
Total SA = Lateral SA + 2 × Base area = \(300 + 2 \times 30 = 300 + 60 = 360\ \text{cm}^2\
Wait — checking options: 360 is option A. Let me recheck — actually answer is A (360). Note: This is correctly 360.
In the Shannon-Weaver model, physical noise refers to mechanical or engineering interference in the communication channel — for example, a crackling microphone, smudges on a printed page, or a loud motorbike interrupting a conversation. Semantic noise, by contrast, is far harder to eliminate. It arises when the sender and receiver do not share the same knowledge level, cultural background, experiences, or beliefs, so the decoded meaning differs from the intended one. Shannon himself was primarily an engineer focused on physical noise, but subsequent scholars extended his model to include semantic interference. Because semantic noise depends on the “field of experience” of each party (a concept later formalised by Schramm), it cannot be fixed by stronger signals alone — it requires shared context and mutual understanding.
Using Gay-Lussac's Law at constant volume:
$\dfrac{P_1}{T_1} = \dfrac{P_2}{T_2}$
$P_1 = 300\ \text{kPa} = 3 \times 10^5\ \text{Pa},\ T_1 = 300\ \text{K}$
$P_2 = 1.2 \times 10^6\ \text{Pa}$
$T_2 = T_1 \times \dfrac{P_2}{P_1} = 300 \times \dfrac{1.2\times10^6}{3\times10^5} = 300 \times 4 = 1200\ \text{K}$
$T_2\ (°C) = 1200 - 273 = \mathbf{927}°\text{C}$
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