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Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
If log2(3x - 1) = 5, find x.
A
2.00
B
3.67
C
8.67
D
11
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
Log2(3x - 1) = 5
Log2(3x - 1) = Log225
Log2(3x - 1) = Log232
3x - 1 = 32
3x = 32 + 1 = 33
x = \(\frac{33}{3}\)
= 11
Source: Myschool Past Questions Archive (Record #46196)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
A sphere of radius rcm has the same volume as cylinder of radius 3cm and height 4cm. Find the value of r
A
\(\frac{2}{3}\)
B
2
C
3
D
6
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
Volume of sphere = Volume of cylinder
i.e. \(\frac{4}{3} \pi r^3 = \pi r^2 h\)
\(\frac{4}{3} \pi r^3 = \pi \times 3^2 \times 4\)
r3 = \(\frac{\pi \times 9 \times 4 \times 3}{4 \pi}\)
r = 3\(\sqrt{27}\)
= 3
Source: Myschool Past Questions Archive (Record #46199)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Express 1975 correct to 2 significant figures
A
20
B
1,900
C
1,980
D
2,000
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #46203)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Diagram
Solution
Examine M' \(\cap\) N from the venn diagram
Attached Figure / Diagram
A
{f, g}
B
{e}
C
{e, f, g}
D
{e, f, g}
medium Difficulty
Verified Correct Answer: Option A
Step-by-Step Mathematical Solution
From the venn diagram given,
M = (a, b, c), N = (c, f, g)
U = (a, b, c, d, e, f, g)
Thus M' \(\cap\) N = (e, f, g) \(\cap\) (c, f, g)
= (f, g)
Source: Myschool Past Questions Archive (Record #46208)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
If 20(mod 9) is equivalent to y(mod 6), find y.
A
1
B
2
C
3
D
4
medium Difficulty
Verified Correct Answer: Option B
Step-by-Step Mathematical Solution
First, reduce 20(mod 9) to its simplest form in mod 9; 9 x 2 + 2 = 2(mod 9)
If 2(mod 9) y(mod 6), then y = 2 by comparism
Source: Myschool Past Questions Archive (Record #46209)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
Simplify \(\frac{(p - r)^2 - r^2}{2p^2 - 4pr}\)
A
\(\frac{1}{2}\)
B
p - 2r
C
\(\frac{1}{p - 2r}\)
D
\(\frac{2p}{p - 2r}\)
medium Difficulty
Verified Correct Answer: Option A
Step-by-Step Mathematical Solution
\(\frac{(p - r)^2 - r^2}{2p^2 - 4pr}\)
= \(\frac{(p - r)(p - r) - r^2}{2p^2 - 4pr}\)\
= \(\frac{p^2 - 2pr + r^2 - r^2}{2p(p - 2r}\)
= \(\frac{p^2 - 2pr}{2p(p - 2r)}\)
= \(\frac{p(p - 2r)}{2p(p - 2r)}\)
= \(\frac{1}{2}\)
Source: Myschool Past Questions Archive (Record #46211)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
The relation y = x2 + 2x + k passes through the point (2,0). Find the value of k
A
- 8
B
- 4
C
4
D
8
medium Difficulty
Verified Correct Answer: Option A
Step-by-Step Mathematical Solution
Y = x2 + 2x + k (given)
y = o when x = 2
thus 0 = 22 + 2 x 2 + k
0 = 4 + 4 + k
given k = -8
Source: Myschool Past Questions Archive (Record #46218)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
The ratio of the exterior angle to the interior angle of a regular polygon is 1:11. How many sides has the polygon?
A
30
B
24
C
18
D
12
medium Difficulty
Verified Correct Answer: Option B
Step-by-Step Mathematical Solution
Let a represent an interior angle; e represent an exterior angle. A section of the polygon is down in the diagram.
\(\frac{e}{a}\) = \(\frac{l}{11}\) given
a = 11e
a + e = 180o(angles on a straight line)
11e + e = 180o
12e = 180o
e = \(\frac{180^o}{12}\)
= 15o
Hence, number of sides
= \(\frac{360^o}{\tect{size of one exterior angle}\)
= \(\frac{360^o}{14^o}\)
= 24
Source: Myschool Past Questions Archive (Record #46223)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
Halima is n years old. Her brother's age is 5 years more than half of her age. How old is her brother?
A
\(\frac{n}{2} + \frac{5}{2}\)
B
\(\frac{n}{2}\) - 5
C
5 - \(\frac{n}{2}\)
D
\(\frac{n}{2}\) + 5
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
Halima's age = n years old
Her brother's age = \(\frac{n}{2}\) + 5
Source: Myschool Past Questions Archive (Record #46225)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
An object is 6m away from the base of a mast. If the angle of depression of the object from the top of the mast is 50o, find, correct to 2 decimal places, the height of the mast.
A
8.60m
B
7.83m
C
7.51m
D
7.15m
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
In the diagram give, \(\alpha\) 50o(alternative angles)
tan\(\alpha\) = \(\frac{h}{6}\)
h = 6tan\(\alpha\)
= 6tan 50o
= 6 x 1.1918
= 7.1508
= 7.15m (2d.p)
Source: Myschool Past Questions Archive (Record #46227)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
(a) Solve : \(7(x + 4) - \frac{2}{3}(x - 6) \leq 2[x - 3(x + 5)]\)
(b) A transport company has a total of 20 vehicles made up of tricycle and taxicabs. Each tricycle carries 2 passengers while each taxicab carries four passengers. If the 20 vehicles carry a total of 66 passengers at a time, how many tricycles does the company have?
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) \(7(x + 4) - \frac{2}{3}(x - 6) \leq 2[x - 3(x + 5)]\)
Multiply through by 3 to clear the fraction :
\(21(x + 4) - 2(x - 6) \leq 6[x - 3(x + 5)]\)
\(21x + 84 - 2x + 12 \leq 6x - 18x - 90\)
\(19x + 96 \leq -12x - 90\)
\(19x + 12x \leq -90 - 96\)
\(31x \leq - 186\)
Hence, \(x \leq -6\).
(b) Let : t represent number of tricycles; and b represent number of taxicabs
Then \(t + b = 20 ... (1)\)
\(2t + 4b = 66 .... (2)\)
From (1), b = 20 - t. Put that into eqtn (2), we have:
\(2t + 4(20 - t) = 2t + 80 - 4t = 66\)
\(80 - 66 = 14 = 2t \)
\(t = 7\)
The transport company has 7 tricycles.
Source: Myschool Past Questions Archive (Record #52443)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
Scores
1
2
3
4
5
6
Frequency
25
30
x
28
40
32
The table shows the outcome when a die is thrown a number of times. If the probability of obtaining a 3 is 0.225;
(a) How many times was the die thrown?
(b) Calculate the probability that a trial chosen at random gives a score of an even number or a prime number.
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) From the table, \(\sum f = x + 155\)
P(obtaining a 3) = \(\frac{\text{no of times a 3 was obtained}}{\sum f}\)
\(\frac{x}{x + 155} = 0.225\)
\(x = 0.255x + (155 \times 0.225)\)
\(x - 0.225x = 34.875 \)
\(0.775x = 34.875\)
\(x = \frac{39.875}{0.775}\)
\(x = 45\)
\(\sum f = 155 + x = 155 + 45 = 200\)
Hence, the die was thrown 200 times.
(b) Set of even numbers = {2, 4, 6}
Set of prime numbers = {2, 4, 5}
Therefore, \(N \cup M = (2, 3, 4, 5, 6)\)
\(n(N \cup M) = 30 + 45 + 28 + 40 + 32 = 175\)
\(P(N \cup M) = \frac{175}{200} = 0.875\)
Source: Myschool Past Questions Archive (Record #52454)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
(a) Find the sum of the Arithmetic Progression (AP) 1, 3, 5,..., 101.
(b) Out of the 95 travellers interviewed, 7 travelled by bus and train only, 3 by train and car only and 8 travelled by all 3 means of transport. The number, x, of travellerswho travelled by bus only was equal to the number who travelled by bus and car only. If 47 people travelled by bus and 30 by train :
(i) represent this information in a Venn diagram;
(ii) calculate the
(1) value of x ; (2) number who travelled by at least two means.
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a)
(b)(i) From the Venn diagram,
x + x + 7 + 8 = n(B)
2x + 15 = 47
2x = 47 - 15 = 32
x = 16
(ii) Number of people who travelled by at least 2 means
= 16 + 7 + 8 + 3 = 34
Source: Myschool Past Questions Archive (Record #52464)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
(a) Using the method of completing the square, solve, correct to 2 decimal places, \(\frac{x - 2}{4} = \frac{x + 2}{2x}\).
(b)
In the diagram, PQRST is a circle with centre O. If PS is a diameter, RS//QT, and < QTS = 52^\circ, find :
(i) < SQT ; (ii) < PQT.
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) \(\frac{x - 2}{4} = \frac{x + 2}{2x}\)
\(2x(x - 2) = 4(x + 2)\)
\(2x^{2} - 4x = 4x + 8\)
\(2x^{2} - 4x - 4x - 8 = 2x^{2} - 8x - 8 = 0\)
Divide through by 2, we have
\(x^{2} - 4x - 4 = 0\)
\(x^{2} - 4x = 4\)
Taking the square of \(\frac{b}{2}\) and add to both sides,
\(x^{2} - 4x + (-2)^{2} = 4 + (-2)^{2}\)
\((x - 2)^{2} = 8\)
\(x - 2 = \pm {\sqrt{8}}\)
\(x = 2 \pm \sqrt{8}\)
\(x = 2 \pm 2.828\)
\(x = 4.828\) or \(x = -0.828\).
Hence, x = 4.83 or -0.83 (2 decimal place).
(b)(i)
In the diagram above, < QRS = 180^\circ - 52^\circ = 128^\circ (opp. angles of a cyclic quadrilateral).
\(x_{1} = x_{2}\) (base angles of isosceles triangle)
\(x_{1} + x_{2} + 128^\circ = 180^\circ\) (sum of angles of a triangle)
\(2x_{2} = 180^\circ - 128^\circ = 52^\circ\)
\(x_{2} = 26^\circ\)
Hence, < SQT = 26^\circ.
(ii) < PQS = 90^\circ (angles in a semi-circle)
Hence, < PQT = 90^\circ - 26^\circ = 64^\circ.
Source: Myschool Past Questions Archive (Record #52466)
Mathematics
WAEC / WASSCE 2016
Number and Numeration
Solution
(a) Find the equation of a straight line which passes through the point (2, -3) and is parallel to the line \(2x + y = 6\).
(b) The operation \(\Delta\) is defined on the set T = {2, 3, 5, 7} by \(x \Delta y = (x + y + xy) mod 8\).
(i) Construct modulo 8 table for the operation \(\Delta\) on the set T.
(ii) Use the the table to find: (a) \(2 \Delta (5 \Delta 7)\) ; (b) \(2 \Delta n = 5 \Delta 7\).
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) First, change the given linear equation to the gradient- intercept form:
\(2x + y = 6 \implies y = 6 - 2x\)
Thus, \(m_{1} = -2, c = 6\). Thus, for a line to be parallel, the gradient \(m_{2} = -2\) (condition for parallelism).
Using \(y - y_{1} = m(x - x_{1})\), we have
\(y - (-3) = -2(x - 2)\)
\(y + 3 = - 2x + 4\)
\(2x + y = 4 - 3 = 1\)
Thus, the line passing through (2, -3) parallel to 2x + y = 6 is 2x + y = 1.
(b) (i)
\(\Delta\)
2
3
5
7
2
0
3
1
7
3
3
7
7
7
5
1
7
3
7
7
7
7
7
7
(ii) (a) \(2 \Delta (5 \Delta 7) = 2 \Delta 7 = 7\)
(b) \(2 \Delta n = 5 \Delta 7\)
\(2 \Delta n = 7\)
By comparison, n = 7.
Source: Myschool Past Questions Archive (Record #52481)