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Mathematics
WAEC / WASSCE 2017
Plane Geometry, Polygons & Circle Theorems
Solution
(a) It takes 8 students two- thirds of an hour to fill 12 tanks with water. How many tanks of water will 4 students fill in one- third of an hour at the same rate?
(b) A chord, 20 cm long, is 12 cm from the centre of the circle. Calculate, correct to one decimal place, the :
(i) angle subtended by the chord at the centre of the circle;
(ii) perimeter of the minor segment cut off by the chord. [Take \(\pi = 3.142\)].
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) \(Time = \frac{2}{3} hour = \frac{2}{3} \times 60 = 40 mins\)
4 students will take \(\frac{8 \times 40}{4} = 80 minutes\)
\(Time = \frac{1}{3} hour = \frac{1}{3} \times 60 = 20 minutes\)
It will take 20 minutes to fill \(\frac{12 \times 20}{80} = 3 tanks\)
(b)
\(\tan (\frac{\theta}{2}) = \frac{10}{12}\)
\(\frac{\theta}{2} = \tan^{-1} (0.8337) = 39.8^\circ\)
\(\theta = 39.8^\circ \times 2 = 79.6^\circ\)
(ii) Perimeter of minor segment = Length of chord + length of arc
But \(r^{2} = 12^{2} + 10^{2}\)
= \(144 + 100 = 244\)
\(r = \sqrt{244} = 15.62 cm\)
Length of arc = \(\frac{79.6}{360} \times 2 \times 3.142 \times 15.62 = 21.71cm\)
Perimeter of minor segment = 20 + 21.71 = 41.71cm
Source: Myschool Past Questions Archive (Record #52385)
Mathematics
WAEC / WASSCE 2017
Fractions, Decimals, Percentages & Approximations
Solution
(a) Using completing the square method, solve, correct to 2 decimal places, the equation \(3y^{2} - 5y + 2 = 0\).
(b) Given that \(M = \begin{pmatrix} 1 & 2 \\ 4 & 3 \end{pmatrix}, N = \begin{pmatrix} m & x \\ n & y \end{pmatrix}\) and \(MN = \begin{pmatrix} 2 & 1 \\ 3 & 4 \end{pmatrix}\), find the matrix N.
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) \(3y^{2} - 5y + 2 = 0\)
\(\frac{3y^{2}}{3} - \frac{5y}{3} = \frac{-2}{3}\)
\(y^{2} - \frac{5}{3}y = \frac{-2}{3}\)
\(\frac{1}{2} of \frac{-5}{3} = \frac{-5}{6}\)
\(y^{2} - \frac{5}{3}y + (-\frac{5}{6})^{2} = \frac{-2}{3} + (\frac{-5}{6})^{2}\)
\((y - (\frac{5}{6}))^{2} = \frac{1}{36}\)
Taking square root of both sides,
\(\sqrt{(y - (\frac{5}{6}))^{2}} = \sqrt{\frac{1}{36}}\)
\(y - \frac{5}{6} =\pm {\frac{1}{6}}\)
\(y = \frac{5}{6} \pm \frac{1}{6}\)
\(y = \frac{5}{6} + \frac{1}{6} = 1.00\) or \(y = \frac{5}{6} - \frac{1}{6} = \frac{2}{3} = 0.67\).
(b) \(M = \begin{pmatrix} 1 & 2 \\ 4 & 3 \end{pmatrix}, N = \begin{pmatrix} m & x \\ n & y \end{pmatrix}\)
\(MN = \begin{pmatrix} m + 2n & x + 2y \\ 4m + 2n & 4x + 2y \end{pmatrix} = \begin{pmatrix} 2 & 1 \\ 3 & 4 \end{pmatrix}\)
\(m + 2n = 2 ... (1)\)
\(4m + 2n = 3 ... (2)\)
Multiplying (1) by 4, we have
\(4m + 8n = 8 ... (3)\)
(3) - (1) : \(8n - 2n = 8 - 2 = 6\)
\(6n = 6 \implies n = 1\)
\(m + 2n = m + 2(1) = m + 2 = 2\)
\(m = 2 - 2 = 0\)
\(x + 2y = 1 ... (1)\)
\(4x + y = 4 ... (2)\)
Multiply (1) by 4,
\(4x + 8y = 4 ... (3)\)
(3) - (2) : \(8y - y = 4 - 4 = 0\)
\(\implies y = 0\)
\(x + 2y = x + 2(0) = x + 0 = 1\)
\(x = 1 - 0 = 1\)
\(\therefore N = \begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix}\).
Source: Myschool Past Questions Archive (Record #52406)
Mathematics
WAEC / WASSCE 2017
Coordinate Geometry
Solution
(a) The operation (*) is defined on the set of real numbers, R, by \(x * y = \frac{x + y}{2}, x, y \in R\).
(i) Evaluate \(3 * \frac{2}{5}\).
(ii) If \(8 * y = 8\frac{1}{4}\), find the value of y.
(b) In \(\Delta ABC, \overline{AB} = \begin{pmatrix} -4 \\ 6 \end{pmatrix}\) and \(\overline{AC} = \begin{pmatrix} 3 \\ -8 \end{pmatrix}\). If P is the midpoint of \(\overline{AB}\), express \(\overline{CP}\) as a column vector.
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) (i) \(3 * \frac{2}{5} = \frac{3 + \frac{2}{5}}{2}\)
= \(\frac{\frac{17}{5}}{2}\)
= \(\frac{17}{10}\)
(ii) \(8 * y = 8\frac{1}{4}\)
\(\frac{8 + y}{2} = \frac{33}{4}\)
\(66 = 32 + 4y \implies 4y = 66 - 32 = 34\)
\(y = \frac{34}{4} = 8.5\)
(b) \(\overrightarrow{AP} = \frac{1}{2}(\overrightarrow{AB})\)
= \(\frac{1}{2} \begin{pmatrix} -4 \\ 6 \end{pmatrix}\)
= \(\begin{pmatrix} -2 \\ 3 \end{pmatrix}\)
Midpoint = \(\overrightarrow{AP} + \overrightarrow{PC} = \overrightarrow{AC}\)
\(\overrightarrow{PC} = \overrightarrow{AC} - \overrightarrow{AP}\)
= \(\begin{pmatrix} 3 \\ -8 \end{pmatrix} - \begin{pmatrix} -2 \\ 3 \end{pmatrix}\)
= \(\begin{pmatrix} 5 \\ -11 \end{pmatrix}\)
\(\overrightarrow{CP} = -1 \times \begin{pmatrix} 5 \\ -11 \end{pmatrix}\)
= \(\begin{pmatrix} -5 \\ 11 \end{pmatrix}\)
Source: Myschool Past Questions Archive (Record #52423)
Physics
WAEC / WASSCE 2017
Newton's Laws, Momentum & Collisions
Solution
Which of the following is the dimension for impulse?
A
MLT\(^{-1}\)
B
MLT\(^{-2}\)
C
MLT
D
ML
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Impulse = Force \(\times\) time
Force has the dimension \(\frac{ML}{T^{2}}\), hence
Impulse= \(\frac{ML}{T^{2}} \times T = \frac{ML}{T}\)
Source: Myschool Past Questions Archive (Record #49912)
Physics
WAEC / WASSCE 2017
Current Electricity & Electric Circuits
Solution
A body accelerates uniformly from rest at 2\(ms^{-2}\). Calculate its velocity when it has travelled a distance of 9m.
A
3.0\(ms^{-1}\)
B
4.5\(ms^{-1}\)
C
6.0\(ms^{-1}\)
D
18.0\(ms^{-1}\)
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Given that \(u = 0ms^{-1}, a = 2ms^{-2}, s = 9m\)
We can use the equation, \(v^{2}=u^{2} +2as\) so that we have,
\(v^{2} = 0^{2} + 2\times 2\times 9\)
\(v^{2} = 36; v= 6.0ms^{-1}\)
Note; u = Initial velocity
v = final velocity
a = acceleration
s = distance covered
Source: Myschool Past Questions Archive (Record #49913)
Physics
WAEC / WASSCE 2017
Current Electricity & Electric Circuits
Solution
Which of the following statements about matter is not correct?
A
Molecules of solids move more freely than molecules of liquids and gases
B
Molecules of solids are more closely packed than those of liquids
C
Energy is required to break the intermolecular forces of attraction between molecules
D
Molecules of liquids move about within the liquid and they are in constant motion
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
All other properties of the different states of matter holds except that the molecules of solids don't move freely due to the fact that the particles in the solids are closely packed so it inhibits free motion.
Source: Myschool Past Questions Archive (Record #49916)
Physics
WAEC / WASSCE 2017
Linear Motion, Projectiles & Kinematics
Solution
A ball is projected horizontally from the top of a tower. Neglecting air resistance, which of the following statements about its motion is/are correct?
I. Vertical acceleration on the ball decreases as it falls
II. The vertical force on the ball remains constant
III. The vertical speed of the ball increases as it falls
A
I only
B
II only
C
I and II only
D
II and III only
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
The body while coming down is acted upon by acceleration due to gravity, hence, the vertical force is constant. Also, at maximum height, the vertical velocity is 0 and then increases as the body comes downward.
Source: Myschool Past Questions Archive (Record #49922)
Physics
WAEC / WASSCE 2017
Scalars, Vectors & Relative Motion
Diagram
Solution
Two forces 100N and 60N act on an object of mass 10kg as illustrated in the diagram above. Neglecting friction, calculate the acceleration of the object.
Attached Figure / Diagram
A
4.0\(ms^{-2}\)
B
13.4\(ms^{-2}\)
C
16.0\(ms^{-2}\)
D
22.6\(ms^{-2}\)
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Resolving 100N into horizontal and vertical
100 sin45 = 0.7071 * 100 = 70.71
100cos45 = 70.71
Vertical forces = 100 - 70.71 → 29.29
Horizontal force = 70.71 + 60 → 130.71
Resultant of vertical and horizontal forces using pythagoras thoerem
Resultant force (F) = m * a
a = F/m → 133.9/10
a = 13.4
Source: Myschool Past Questions Archive (Record #49934)
Physics
WAEC / WASSCE 2017
Equilibrium of Forces, Moments & Flotation
Solution
A body weighing 14N in air is partially immersed in water. If the mass of water displaced in the process is 200g, calculate the upthrust on the body. [g=10\(m/s^{2}\)]
A
2.0N
B
3.0N
C
3.5N
D
7.0N
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Upthrust = weight of liquid displaced
= mass of liquid displaced \(\times\) acceleration due to gravity
= \(\frac{200}{1000} \times 10\)
= 2N
Source: Myschool Past Questions Archive (Record #49940)
Physics
WAEC / WASSCE 2017
Atomic, Quantum, Nuclear Physics & Electronics
Which of the following processes is not a surface phenomenon?
A
Condensation
B
Evaporation
C
Photo Emission
D
Thermionic Emission
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #49946)
Physics
WAEC / WASSCE 2017
Units, Measurements & Dimensional Analysis
Solution
A chemical balance is used for measuring
A
volume
B
mass
C
thickness
D
density
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
It is a type of beam balance with great precision, and it can pick up the slightest mass placed on it.
Source: Myschool Past Questions Archive (Record #49950)
Physics
WAEC / WASSCE 2017
Current Electricity & Electric Circuits
Diagram
A body is whirled round a circular path at constant speed. Which of the following diagrams correctly indicates the direction of the body's velocity (v) and its acceleration (a)?
Attached Figure / Diagram
A
I
B
II
C
III
D
IV
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #49956)
Physics
WAEC / WASSCE 2017
Current Electricity & Electric Circuits
Solution
A motorist travelling at 72\(kmh^{-1}\) had his eyes shut for 0.4s during a hard sneeze. Calculate the distance covered by him during this time interval.
A
50.0m
B
28.8m
C
18.0m
D
8.0m
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Convert velocity from \(kmh^{-1}\) to \(ms^{-1}\), by multiplying \(\frac{1000}{3600}\),
\(72 \times \frac{1000}{3600}\) = \(20ms^{-1}\)
Therefore, distance covered in 0.4s = \(20 \times 0.4 = 8m\)
Source: Myschool Past Questions Archive (Record #49958)
Physics
WAEC / WASSCE 2017
Linear Motion, Projectiles & Kinematics
Solution
The angle at which a projectile must be fired to cover maximum range is
A
30°
B
45°
C
60°
D
90°
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
The formula is \(\frac{v^{2}sin2\theta}{g}\)
And the sine graph is highest at 1 with its inverse as 90^\circ. Hence, \(2\theta\) = 90^\circ
\(\theta\) = 45^\circ
Source: Myschool Past Questions Archive (Record #49961)
Physics
WAEC / WASSCE 2017
Scalars, Vectors & Relative Motion
Solution
A body can undergo the following types of motion except
A
random
B
rotational
C
translational
D
relative
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Relative motion is the calculation of the motion of an object with regard to some other moving object. Hence, relative motion is not a type of motion.
Source: Myschool Past Questions Archive (Record #49964)