Mathematics 2018 Jamb Examination
Mathematics 2018 Jamb Examination
Question 31
A man stands on a tree 150cm high and sees a boat at an angle of depression of 74°. Find the distance of the boat from the base of the tree.
The angle of depression is equal to the angle of elevation from the boat to the man. Let \( \displaystyle d \) be the distance from the base. Using trigonometry:
\[ \displaystyle \tan 74^\circ = \frac{150}{d} \]
\[ \displaystyle d = \frac{150}{\tan 74^\circ} = \frac{150}{3.487} \approx 43\text{cm} \]
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Question 32
Integrate the expression \( \displaystyle 6x^2 - 2x + 1 \)
Apply the power rule for integration \( \displaystyle \int x^n dx = \frac{x^{n+1}}{n+1} \):
\( \displaystyle \int 6x^2 dx = \frac{6x^3}{3} = 2x^3 \)
\( \displaystyle \int -2x dx = -\frac{2x^2}{2} = -x^2 \)
\( \displaystyle \int 1 dx = x \) \[ \displaystyle \int (6x^2 - 2x + 1) dx = 2x^3 - x^2 + x + c \]
\( \displaystyle \int 6x^2 dx = \frac{6x^3}{3} = 2x^3 \)
\( \displaystyle \int -2x dx = -\frac{2x^2}{2} = -x^2 \)
\( \displaystyle \int 1 dx = x \) \[ \displaystyle \int (6x^2 - 2x + 1) dx = 2x^3 - x^2 + x + c \]
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Question 33
In how many ways can the letters LEADER be arranged?
The word LEADER has 6 letters. We check for repeated letters:
- E appears 2 times.
The number of unique arrangements is calculated as:
\[ \displaystyle \frac{6!}{2!} = \frac{720}{2} = 360 \]
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Question 34

In the figure below, /MX/ = 8cm, /XN/ = 12cm, /NZ/ = 4cm and ∠XMN = ∠XZY. Calculate /YM/
Since \( \displaystyle \angle XMN = \angle XZY \) and \( \displaystyle \angle X \) is common, triangles XMN and XZY are similar.
Using the ratio of corresponding sides:
\[ \displaystyle \frac{MX}{XZ} = \frac{XN}{XY} \]
Given \( \displaystyle XZ = XN + NZ = 12 + 4 = 16\text{cm} \):
\[ \displaystyle \frac{8}{16} = \frac{12}{XY} \implies \frac{1}{2} = \frac{12}{XY} \implies XY = 24\text{cm} \]
\( \displaystyle YM = XY - MX = 24 - 8 = 16\text{cm} \)
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Question 35
Express 495g as a percentage of 16.5kg
First, convert both values to the same unit (grams):
\[ \displaystyle 16.5\text{kg} = 16.5 \times 1000 = 16500\text{g} \]
Now calculate the percentage:
\[ \displaystyle \frac{495}{16500} \times 100 = \frac{495}{165} = 3\% \]
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Question 36
Evaluate \( \displaystyle (2\sqrt{3} - 4)(2\sqrt{3} + 4) \)
This is a difference of two squares in the form \( \displaystyle (a - b)(a + b) = a^2 - b^2 \).
\[ \displaystyle (2\sqrt{3})^2 - 4^2 \]
\[ \displaystyle (4 \times 3) - 16 \]
\[ \displaystyle 12 - 16 = -4 \]
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Question 37
Find the equation of the tangent at the point (2, 0) to the curve \( \displaystyle y = x^2 - 2x \)
First, find the gradient of the curve by differentiating:
\[ \displaystyle \frac{dy}{dx} = 2x - 2 \]
At the point (2, 0), the gradient \( \displaystyle m \) is:
\[ \displaystyle m = 2(2) - 2 = 2 \]
Using the equation of a straight line \( \displaystyle y - y_1 = m(x - x_1) \):
\[ \displaystyle y - 0 = 2(x - 2) \implies y = 2x - 4 \]
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Question 38
Evaluate \( \displaystyle \log_2 8 - \log_3 \frac{1}{9} \)
Solve each logarithm separately:
\( \displaystyle \log_2 8 = \log_2 2^3 = 3 \)
\( \displaystyle \log_3 \frac{1}{9} = \log_3 3^{-2} = -2 \)
Subtracting the two values: \[ \displaystyle 3 - (-2) = 3 + 2 = 5 \]
\( \displaystyle \log_2 8 = \log_2 2^3 = 3 \)
\( \displaystyle \log_3 \frac{1}{9} = \log_3 3^{-2} = -2 \)
Subtracting the two values: \[ \displaystyle 3 - (-2) = 3 + 2 = 5 \]
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Question 39
Tanθ is positive and Sinθ is negative. In which quadrant does θ lie?
We use the CAST rule:
- 1st Quadrant: All (Sin, Cos, Tan) are positive.
- 2nd Quadrant: Only Sin is positive.
- 3rd Quadrant: Only Tan is positive (meaning Sin and Cos are negative).
- 4th Quadrant: Only Cos is positive.
Since Tanθ is positive and Sinθ is negative, the angle must be in the Third Quadrant.
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Question 40

Use the quadratic equation curve to answer this question: What is the minimum value of the graph?
The minimum value of a quadratic graph (parabola) is the y-coordinate of its lowest point, also known as the vertex. Looking at the provided graph, the curve dips to its lowest point at approximately \( \displaystyle y = -5.3 \) on the vertical axis.
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