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Mathematics
WAEC / WASSCE 2019
Statistics and Probability
Solution
A survey of 40 students showed that 23 students study Mathematics, 5 study Mathematics and Physics, 8 study Chemistry and Mathematics, 5 study Physics and Chemistry and 3 study all the three subjects. The number of students who study Physics only is twice the number who study Chemistry only.
(a) Find the number of students who study:
(i) only Physics.
(ii) only one subject
b) What is the probability that a student selected at random studies exactly 2 subjects?
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
Let \(\mu\) = 40 n(M) = 23, n(M \(\cup\) P) = 5, n(M \(\cup\) C) = 8, n(P \(\cup\) C) = 5, n(M \(\cup\) P \(\cup\) C) = 3, n(C) only = x and n(P) only = 2x
(a)(i) We have 13 + 2 + 3 + 5 + x + 2 + 2x = 40 and solving for x will yield x = 5, so that the number of students that studied only Physics = 2(5) = 10
(a)(ii) The number of students that studied only one subject is 13 + 10 + 5 = 28
(b) The probability that a student selected at random studies exactly two subjects = \(\frac{5 + 2 + 2}{40} = \frac{9}{48}\) or 0.225
Source: Myschool Past Questions Archive (Record #56459)
Mathematics
WAEC / WASSCE 2019
Algebra
Solution
a) A twenty - kilogram bag of rice is consumed by m number of boys in 10 days. When four more boys joined them, the same quantity of rice lasted only 8 days. If the rate of consumption is the same, find the value of m.
(b) If \(\frac{5}{6}\) of a number is 10 greater than \(\frac{1}{3}\) of it. find the number
(c) Find the equation of the line which passes through the points (2, \(\frac{1}{2}\)) and (-1, -\(\frac{1}{2}\)
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) it will take 1 boy 10m days and when 4 more boys are added, it will take 8(m + 4) days. Since the rate of consumption was the same, then 10m = 8m + 32 and when solves, m = 16
(b) Let x be the number. so that \(\frac{5}{6}\)x = 10 + \(\frac{1}{2}\)x and multiplying through by 6 to get 5x = 60 + 2x. This was solved to get x = 20
(c) Let the gradient be m = \(\frac{\frac{1}{2} - (\frac{1}{2})}{2 - (-1)} = \frac{2}{3}\). The equation of the lines is y - y\(_1\) = m(x - x\(_1\)). Sunstituting for x\(_1\) and y\(_1\)
y - (\(\frac{-1}{2}\)) = \(\frac{1}{2}\)(x - (-1)) and this can be simplified to y = \(\frac{1}{3}x - \frac{1}{6}\) or 2x - 6y - 1 = 0
Source: Myschool Past Questions Archive (Record #56463)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Solution
A ladder 11m long leans against a vertical wall at an angle of 75\(^o\) to the ground. The ladder is the pushed 0.2 m up the wall.
(a) Illustrate the information in a diagram.
(b) Find correct to the nearest whole number, the:
(i) new angle which the ladder makes with the ground:
(ii) distance the foot of the ladder has moved from its original position.
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) The required diagram was
(b)(i) we have sin 75\(^o\) = \(\frac{x}{11}\) and this will give x = 10.625m. Since the ladder has moved up by 0.2 , the new point where the ladder touches the wall is 0.2 + 10.625 = 10.825m.
Then sin\(\theta\) = \(\frac{10.825}{11}\)
Sin\(\theta\) = 0.9841 and \(\theta\) = sin\(^{-1}\)(0.9841) = 79.77\(^o\) = 80\(^o\)
(b)(ii) Cos 75\(^o\) = \(\frac{y}{11}\) so that y = 2.2847m
Similarity, cos 79.77 = \(\frac{q}{11}\) and q = 1.9536m. Therefore, the distance the ladder was dragged = 2.8470 - 1.9536 = 0.8934m = 1m
Source: Myschool Past Questions Archive (Record #56476)
Mathematics
WAEC / WASSCE 2019
Algebra
Solution
(a) Copy and complete the table of values for the relation y = 4x\(^2\) - 8x - 21, for -2.0 \(\leq\) x \(\leq\) 4.0
x
-2.0
-1.5
-1.0
0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
y
11
-9
-21
-24
-21
-9
0
(b) Using a scale of 2cm to 1 unit on the x-axis and 2cm to 5 units on the y-axis, draw the graph for the relation y = 4x\(^2\) - 8x - 21
(ii) Use the graph to find the solution set of
(\(\alpha\)) 4x\(^2\) - 8x = 3;
(\(\beta\)) 4x\(^2\) - 7x - 21 = 0
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) They completed the table of values as shown
x
-2.0
-1.5
-1.0
0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
y
11
0
-9
-16
-21
-24
-25
-24
-21
-16
-9
0
11
(b)(i) The graph
(b)(ii)(\(\alpha\), deduce that 4x\(^2\) - 8x - 21 = 3 - 21 so that y = -18. From the graph, the point of intersection of y = -18 and y = 4x\(^2\) - 8x - 21 was atx = {-0.35 \(\pm\) 0.1, 2.3 \(\pm\) 0.1}
(b)(ii)(\(\beta\)), the equation 4x\(^2\) - 8x - 21 = 0 which can be written as 4x\(^2\) - x - 7x - 21 = -x. This implies that 4x\(^2\) - 8x - 21 = -x.
But, y = 4x\(^2\) - 8x - 21 so that y = -x, Next was to draw the line y = -x and from the graph, the point of intersection with the curve y = 4x\(^2\) - 8x - 21 was at x = {3.3 \(\pm\) 0.1, -1.6 \(\pm\) 0.1}
Source: Myschool Past Questions Archive (Record #56478)
Mathematics
WAEC / WASSCE 2019
Number and Numeration
Solution
(a) The curved surface areas of two cones are equal. The base radius of one is 5 cm and its slant height is 12cm. calculate the height of the second cone if its base radius is 6 cm.
(b) Given the matrices A = \(\begin{pmatrix} 2 & 5 \\ -1 & -3 \end{pmatrix}\) and B = \(\begin{pmatrix} 3 & -2 \\ 4 & 1 \end{pmatrix}\), find:
(i) BA;
(ii) the determinant of BA.
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a) since the curved surface areas were the same, it was expected that they have 5 x 12\(pi\) = 6 \(\pi\)l and solving for the slant height to get l = 10 cm.
Then by the use of Pythagoras theorem, the height of the second cone is h\(^2\) = 10\(^2\) - 6\(^2\) and when simplified will result in h = 8 cm.
(b(i), they were to find BA = \(\begin{pmatrix} 3 & -2 \\4 & 1\end{pmatrix}\) \(\begin{pmatrix} 2 & 5 \\ -1 & -3\end{pmatrix}\) = \(\begin{pmatrix} 8 & 21 \\ 7 & 17 \end{pmatrix}\)
(b)(ii), the determinant of BA = (8 x 17) - (21 x 7) = 136 - 147 = -11
Source: Myschool Past Questions Archive (Record #56479)
Mathematics
WAEC / WASSCE 2019
Number and Numeration
Solution
(a) Given that 110\(_x\) - 40\(_{five}\). find the value of x
(b) Simplify \(\frac{15}{\sqrt{75}} + \(\sqrt{108}\) + \(\sqrt{432}\), leaving the answer in the form a\(\sqrt{b}\), where a and b are positive integers.
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a)110\(_x\) - 4\(0_5\)
1 x \(x^2}\) + 1 x \(x^1\) + 0 x \(x^o\)
x = 4 x 5\(^1\) + 0 x 5\(^o\)
x\(^2\) + x = 4 x 5 + 0
x\(^2\) + x - 20 = 0
(x - 4)(x + 5) = 0
x - 4 = 0 or x + 5 = 0
x = 4 or x = -5
x = 4
(b) Simplify \(\frac{15}{\sqrt{75}}\) + \(\sqrt{108}\) + \(\sqrt{432}\)
= \(\frac{15}{\sqrt{25 \times 3}}\) + \(\sqrt{36 \times 3}\)
= \(\frac{15}{5 \sqrt{3}\) + 6\(\sqrt{3}\) + 12\(\sqrt{3}\)
= \(\frac{15 \sqrt{3}}{15 \times \sqrt{3} \times \sqrt{3}}\) + 18\(\sqrt{3}\)
= \(\frac{15\sqrt{3}}{15}\) + 18\(\sqrt{3}\)
\(\sqrt{3}\) + 18\(\sqrt{3}\) = 19\(\sqrt{3}\)
Source: Myschool Past Questions Archive (Record #56486)
Mathematics
WAEC / WASSCE 2019
Geometry and Trigonometry
Solution
(a)
In the diagram. \(\over{Rs}\) and \(\over{RT}\) are tangent to the circle with centre O, < TUS = 68\(^o\), < SRT = x and < UTO = y. Find the value of x.
(b) Two tanks A and B are filled to capacity with diesel. Tank A holds 600 litres diesel more than tank B. If 100 litres of diesel was pumped cut of each tank, tank A would then contain 3 times as much as tank B. Find the capacity of each tank.
medium Difficulty
Verified Correct Answer: Option
Step-by-Step Mathematical Solution
(a). < SOT = 2 < SOT = 2 x 68^\circ =136.
Observe that < OSR = < OTR = 90\(^o\)
So that < OSR + x + < OTR + < SOT = 360\(^o\). Next is to substitute and simplified to get x + 316\(o\) = 360\(o\) so that x = 44\(o\)
(b) If we let capacity of tank A = a and capacity of tank B = b, then
a = 600 + b......(1)
a - 100 = 3(b - 100)
a = 3b - 200........(2)
Substituting (2) into (1) yielded 3b - 200 = 600 + b and solving for b, b = 400.
Therefore. Capacity of tank B = 400litres
Substituting b in (1) yielded A = 600 + 400 = 1000
Capacity of A =1000.
Source: Myschool Past Questions Archive (Record #56488)
Mathematics
WAEC / WASSCE 2019
Number and Numeration
Solution
Express, correct to three significant figures, 0.003597.
A
0.359
B
0.004
C
0.00360
D
0.00359
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
0,00 3597 = 0.00360 to 3 s.f
Source: Myschool Past Questions Archive (Record #57092)
Mathematics
WAEC / WASSCE 2019
Number and Numeration
Solution
Evaluate: (0.064)\(^{-\frac{1}{3}}\)
A
\(\frac{5}{2}\)
B
\(\frac{2}{5}\)
C
-\(\frac{2}{5}\)
D
-\(\frac{5}{2}\)
medium Difficulty
Verified Correct Answer: Option A
Step-by-Step Mathematical Solution
(0.064)\(^{- \frac{1}{3}}\)
= (\(\frac{64}{1000}\))\(^{-\frac{1}{3}}\)
= 3\(\sqrt{\frac{1000}{64}}\)
= \(\frac{10}{4}\)
= \(\frac{5}{2}\)
Source: Myschool Past Questions Archive (Record #57094)
Mathematics
WAEC / WASSCE 2019
Number and Numeration
Solution
Solve: \(\frac{y + 1}{2} - \frac{2y - 1}{3}\) = 4
A
y = 19
B
y = -19
C
y = -29
D
y = 29
medium Difficulty
Verified Correct Answer: Option B
Step-by-Step Mathematical Solution
\(\frac{y + 1}{2} - \frac{2y - 1}{3}\) = \(\frac{4}{1}\)
- \(\frac{3(y + 1) - 2(2y - 1)}{6} = \frac{4}{1}\)
3y + 3 - 4y + 2 = 24
- y + 5 = 24
- y = 24 - 5 = 19
y = - 19
Source: Myschool Past Questions Archive (Record #57098)
Mathematics
WAEC / WASSCE 2019
Number and Numeration
Solution
Simplify, correct to three significant figures, (27.63)\(^2\) - (12.37)\(^2\)
A
614
B
612
C
611
D
610
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
(27.63)\(^2\) - (12.37)\(^2\)
= (27.63 + 12.37)(27.63 - 12.37)
= 40 x 15.26
= 610
Source: Myschool Past Questions Archive (Record #57100)
Mathematics
WAEC / WASSCE 2019
Number and Numeration
Solution
If 7 + y = 4 (mod 8), find the least value of y, 10 \(\leq y \leq 30\)
A
11
B
13
C
19
D
21
medium Difficulty
Verified Correct Answer: Option B
Step-by-Step Mathematical Solution
7 + y = 4 (mod 8)
y = 4 - 7 (mod 8)
y = -3 + 8 (mod 8)
y = 5 + 8 (mod 8)
y = 13
Source: Myschool Past Questions Archive (Record #57102)
Mathematics
WAEC / WASSCE 2019
Number and Numeration
Solution
Evaluate; \(\frac{\log_3 9 - \log_2 8}{\log_3 9}\)
A
-\(\frac{1}{3}\)
B
\(\frac{1}{2}\)
C
\(\frac{1}{3}\)
D
-\(\frac{1}{2}\)
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
\(\frac{\log_3 9 - \log_2 8}{\log_3 9}\)
= \(\frac{\log_3 3^2 - \log_2 2^3}{\log_3 3^2}\)
= \(\frac{2 -3}{2}\)
= \(\frac{-1}{2}\)
Source: Myschool Past Questions Archive (Record #57125)
Mathematics
WAEC / WASSCE 2019
Number and Numeration
Solution
If 23\(_y\) = 1111\(_{\text{two}}\), find the value of y
A
4
B
5
C
6
D
7
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
23\(_y\) = 1111\(_{\text{two}}\),
2 x y\(^1\) + 3 x y\(^0\) = 1 x 2\(^3\) + 1 x 2\(^1\) + 1 x 2\(^o\)
2y + 3 = 8 + 4 + 2 + 1
2y + 3 = 15
\(\frac{2y}{2}\)
\(\frac{12}{2}\)
y = 6
Source: Myschool Past Questions Archive (Record #57128)
Mathematics
WAEC / WASSCE 2019
Algebra
Solution
If 6, P, and 14 are consecutive terms in an Arithmetic Progression (AP), find the value of P.
A
9
B
10
C
6
D
8
medium Difficulty
Verified Correct Answer: Option B
Step-by-Step Mathematical Solution
6, p, 14
14 - p = p - 6
14 + 6 = p - 6
14 + 6 = p + p
\(\frac{2p}{2}\)
= \(\frac{20}{2}\)
p = 10
Source: Myschool Past Questions Archive (Record #57150)