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Total cost = (negative cost) + (first 10 prints) + (next 10 prints)
Total $= x + 10 \cdot \frac{3x}{5} + 10 \cdot \frac{x}{5} = 45$
$x + \frac{30x}{5} + \frac{10x}{5} = 45$
$x + 6x + 2x = 45$
$9x = 45$
$x = 5$
Therefore $x = 5$ dollars.
Wait, but the marked answer is A (index 0, value 3). Let me verify: if $x = 3$:
Total $= 3 + 10(\frac{9}{5}) + 10(\frac{3}{5}) = 3 + 18 + 6 = 27 \neq 45$
If $x = 5$: Total $= 5 + 10(3) + 10(1) = 5 + 30 + 10 = 45$ ✓
The mathematically correct answer is $x = 5$ (option D, index 3).
\(77 - 50 = 27\)... rechecking: \(77 \times 144 = 11088\), \(11138 - 11088 = 50\). So we add \(77 - 50 = 27\). Since 27 is not among the options, re-check: \(77 \times 145 = 11165\), \(11165 - 11138 = 27\). Answer key gives A (9). Students should verify by direct division.
In 1980, the number of dollars of advertising revenue was how many times as great as the average daily circulation?
[Note: From the graph, in 1980 advertising revenue was $36 million and average daily circulation was 180,000]
Advertising revenue in 1980 = $36 million = $36{,}000{,}000
Average daily circulation = 180,000
Ratio $= \frac{36{,}000{,}000}{180{,}000} = \frac{36{,}000{,}000}{180{,}000} = \frac{360}{1.8} = 200$
Therefore, the advertising revenue was 200 times the daily circulation.
However, checking answer index 3 (which is option D with value 20), there may be a unit issue. Let me recalculate considering if the question means something different... If advertising revenue is $36 million and circulation is 180,000, then $36{,}000{,}000 \div 180{,}000 = 200$.
The correct mathematical answer is 200, but if the marked answer is D (index 3, value 20), there may be an interpretation issue with the original problem.
Evaluate: $\displaystyle\lim_{x\to\frac{\pi}{2}}\dfrac{\cot x - \cos x}{(\pi - 2x)^3}$
Let $x = \dfrac{\pi}{2}-t$ so as $x\to\dfrac{\pi}{2}$, $t\to0$.
$\cot x = \cot\!\left(\tfrac{\pi}{2}-t\right) = \tan t$, $\cos x = \sin t$, $\pi-2x = 2t$
$\lim_{t\to0}\dfrac{\tan t - \sin t}{8t^3} = \lim_{t\to0}\dfrac{\sin t(1-\cos t)}{8t^3\cos t}$
$= \lim_{t\to0}\dfrac{\sin t}{t}\cdot\dfrac{1-\cos t}{t^2}\cdot\dfrac{1}{8\cos t} = 1\cdot\dfrac{1}{2}\cdot\dfrac{1}{8} = \mathbf{\dfrac{1}{16}}$
Official answer is $\dfrac{1}{16}$ (index 1). Rechecking: $\dfrac{1}{2}\cdot\dfrac{1}{8}=\dfrac{1}{16}$.
The recorded value $3.50 \text{ cm}$ has a precision of $0.01 \text{ cm}$. We must find an instrument with a least count (LC) of $0.01 \text{ cm}$.
- Option A: $LC = \frac{1 \text{ mm}}{100} = 0.01 \text{ mm} = 0.001 \text{ cm}$
- Option B: $LC = \frac{1 \text{ mm}}{50} = 0.02 \text{ mm} = 0.002 \text{ cm}$
- Option C: $LC = 0.1 \text{ cm}$
- Option D: $1 \text{ MSD} = \frac{1 \text{ cm}}{10} = 0.1 \text{ cm}$. Since $10 \text{ VSD} = 9 \text{ MSD}$, $1 \text{ VSD} = 0.9 \text{ MSD}$. $LC = 1 \text{ MSD} - 1 \text{ VSD} = 0.1 \text{ MSD} = 0.01 \text{ cm}$.
Thus, Option D matches the required precision.
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