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Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
Simplify: \(\sqrt{108} + \sqrt{125} - \sqrt{75}\)
A
\(\sqrt{3} + 5\sqrt{5}\)
B
\(6 \sqrt{3} - 5 \sqrt{5}\)
C
\(6 \sqrt{3} + \sqrt{2}\)
D
\(6\sqrt{3} - \sqrt{2}\)
medium Difficulty
Verified Correct Answer: Option A
Step-by-Step Mathematical Solution
\(\sqrt{108} + \sqrt{125} - \sqrt{75}\)
= \(\sqrt{3 \times 36} + \sqrt{5 \times 25} - \sqrt{3 \times 25}\)
= \(6 \sqrt{3} + 5 \sqrt{5} - 5 \sqrt{3}\)
= \(\sqrt{3} + 5\sqrt{5}\)
Source: Myschool Past Questions Archive (Record #49030)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
Evaluate: \((64^{\frac{1}{2}} + 125^{\frac{1}{3}})^2\)
A
121
B
144
C
169
D
196
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
\([64^{\frac{1}{2}} + 125^{\frac{1}{3}}]^2\) = \([\sqrt{64} + \sqrt[3] {125}]^2\)
\([8 + 5]^2\) = \([13]^2\)
= 169
Source: Myschool Past Questions Archive (Record #49034)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
Find the value of x for which \(32_{four} = 22_x\)
A
three
B
five
C
six
D
seven
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
\(32_4 = 22_x\)
\(3 \times 4^1 + 2 \times 4^o\) = \(2 \times x^1 + 2 \times x^o\)
12 + 2 x 1 = 2x + 2 x 1
14 = 2x + 2
14 - 2 = 2x
12 = 2x
x = \(\frac{12}{2}\)
x = 6
Source: Myschool Past Questions Archive (Record #49044)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
There are 250 boys and 150 girls in a school, if 60% of the boys and 40% of the girls play football, what percentage of the school play football?
A
40.0%
B
42.2%
C
50.0%
D
52.5%
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
Population of school = 250 + 150 = 400
60% of 250 = \(\frac{\text{60%}}{\text{100%}}\) x 250 = 150
40% of 150 = \(\frac{\text{40%}}{\text{100%}}\) x 150 = 60
Total number of students who plays football;
150 + 60 = 210
Percentage of school that play football;
\(\frac{210}{400}\) x 100% = 52.5%
Source: Myschool Past Questions Archive (Record #49223)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
If \(\log_{10}\)(6x - 4) - \(\log_{10}\)2 = 1, solve for x.
A
2
B
3
C
4
D
5
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
\(\log_{10}\)(6x - 4) - \(\log_{10}\)2 = 1
\(\log_{10}\)(6x - 4) - \(\log_{10}\)2 = \(\log_{10}\)10
\(\log_{10}\)\(\frac{6x - 4}{2}\) - \(\log_{10}\)10
\(\frac{6x - 4}{2}\) = 10
6x - 4 = 2 x 10
= 20
6x = 20 + 4
6x = 20
x = \(\frac{24}{6}\)
x = 4
Source: Myschool Past Questions Archive (Record #49228)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
If F = \(\frac{9}{5}\)C + 32, find C when F = 98.6
A
30
B
37
C
39
D
41
medium Difficulty
Verified Correct Answer: Option B
Step-by-Step Mathematical Solution
F = \(\frac{9}{5}\)C + 32
When F = 98.6
98.6 = \(\frac{9}{5}\)C + 32
98.6 - 32 = \(\frac{9}{5}\)C
66.6= \(\frac{9}{5}\)C
66.6 x 5 = 9C
C = \(\frac{66.6 \times 5}{9}\)
= 37
Source: Myschool Past Questions Archive (Record #49229)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
If y + 2x = 4 and y - 3x = -1, find the value of (x + y)
A
3
B
2
C
1
D
-1
medium Difficulty
Verified Correct Answer: Option A
Step-by-Step Mathematical Solution
y + 2x = 4 .....(1)
y - 3x = -1 ......(2)
Subtract (2) from (1)
2x - (-3x) = 4 - (-1)
2x + 3x = 4 + 1
5x = 5
X = \(\frac{5}{5}\)
= 1
Substitute 1 for x in (1);
y + 2(1) = 4
y + 2 = 4
y = 4 - 2 = 2
Hence, (x + y) = (1 + 2)
= 3
Source: Myschool Past Questions Archive (Record #49232)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
Simplify; \(\frac{2 - 18m^2}{1 + 3m}\)
A
\(2 (1 + 3m)\)
B
\(2 (1 + 3m^2)\)
C
\(2(1 - 3m)\)
D
\(2(1 - 3m^2)\)
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
\(\frac{2 - 18m^2}{1 + 3m}\) = \(\frac{2(1 - 9)m^2}{1 + 3m}\)
= \(\frac{2(1 + 3m)(1 - 3m)}{1 + 3m}\)
= \(2(1 - 3m)\)
Source: Myschool Past Questions Archive (Record #49252)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
The surface area of a sphere is \(\frac{792}{7} cm^2\). Find, correct to the nearest whole number, its volume. [Take \(\pi = \frac{22}{7}\)]
A
113\(cm^3\)
B
131\(cm^3\)
C
311\(cm^3\)
D
414\(cm^3\)
medium Difficulty
Verified Correct Answer: Option A
Step-by-Step Mathematical Solution
Surface area of a sphere = \(4 \pi r^2\)
\(4 \pi r^2\) = \(\frac{792}{7}cm^2\)
4 x \(\frac{22}{7}\) x \(r^2\) = \(\frac{792}{7}\)
\(r^2\) = \(\frac{792}{7}\) x \(\frac{7}{4 \times 22}\)
= 9
r = \(\sqrt{9}\)
= 3cm
Hence, volume of sphere
= \(\frac{4}{3} \pi r^3\)
= \(\frac{4}{3} \times \frac{22}{7} \times 3 \times 3 \times 3 \)
= \(\frac{4 \times 22 \times 9}{7}\)
\(\approx\) = 113.143
= 113\(cm^3\) (to the nearest whole number)
Source: Myschool Past Questions Archive (Record #49272)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
If M and N are the points (-3, 8) and (5, -7) respectively, find |MN|
A
8 units
B
11 units
C
15 units
D
17 units
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
|MN| = \(\sqrt{(x_1 - x_2)^2 + (y_1 - y_2)^2}\)
= \(\sqrt{(-3 -5)^2 + (8 - 7)^2}\)
= \(\sqrt{(-8)^2 + (8 + 7)^2}\)
= \(\sqrt{64 + (15)^2}\)
= \(\sqrt{64 + 225}\)
= \(\sqrt{289}\)
= 17 units
Source: Myschool Past Questions Archive (Record #49348)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
The total surface area of a hemispher is 75\(\pi cm^2\). Find the radius.
A
5.0 cm
B
7.0 cm
C
8.5 cm
D
12.0 cm
medium Difficulty
Verified Correct Answer: Option A
Step-by-Step Mathematical Solution
Total surface area of hemisphere is
3\(\pi r^2\) = 75\(\pi cm^2\)
\(r^2\) = \(\frac{75 \pi}{3 \pi}\)
\(r^2\) = 25
r = \(\sqrt{25}\)
r = 5cm
Source: Myschool Past Questions Archive (Record #49360)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
Find the value of x for which \(\frac{x - 5}{x(x - 1)}\) is undefined.
A
0 or 5
B
-5 or 5
C
-11 or 5
D
0 or 1
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
The expression \(\frac{x - 5}{x(x - 1)}\) is undefined when
x(x - 1) = 0
either x = 0 or x - 1 = 0
Hence, x = 0 or x = 1
Source: Myschool Past Questions Archive (Record #49364)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
Factorise completely the expression
\((x + 2)^2\) - \((2x + 1)^2\)
A
(3x + 2)(1 - x)
B
(3x + 2)(2x + 1)
C
3\((x + 2)^2\)
D
3(x + 1)(1 - x)
medium Difficulty
Verified Correct Answer: Option D
Step-by-Step Mathematical Solution
\((x + 2)^2\) - \((2x + 1)^2\)
= \((x^2 + 4x + 4) - (4x^2 + 4x + 1)\)
= \(x^2 \) + 4x + 4 - 4 \(x^2 \) - 4x - 1
= -3 \(x^2 \) + 3
= 3 - 3 \(x^2 \)
= 3(1 - \(x^2 \))
= 3(1 + x)(1 - x)
Source: Myschool Past Questions Archive (Record #49387)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
If 3x\(^o\) 4(mod 5), find the least value of x
A
1
B
2
C
3
D
4
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
3x \(\equiv\) 4(mod 5)
In modulo 5, multiples of 5 that give solution to the given equation are 5, 20, 35, 50,... but 5 will yield the leaast value of x.
Thus; 3x = 4 + 5 = 9
x = \(\frac{9}{3}\)
x = 3
Source: Myschool Past Questions Archive (Record #49402)
Mathematics
WAEC / WASSCE 2018
Number and Numeration
Solution
Find the inter-quartile range of 1, 3, 4, 5, 8, 9, 10, 11, 12, 14, 16
A
6
B
7
C
8
D
9
medium Difficulty
Verified Correct Answer: Option C
Step-by-Step Mathematical Solution
\(Q_1 = \frac{1}{4}\) (N + 1)th
\(\frac{1}{4} \times 12^{th}\) no.
= 3rd no (\(\cong\) 4)
\(Q_3 = \frac{3}{4}\) (N + 1)th
= \(\frac{3}{4}\) x 12th no.
= 9th no. (\(\cong\) 12)
Hence, interquartile range
= \(Q_3 - Q_1\)
= 12 - 4
= 8
Source: Myschool Past Questions Archive (Record #49403)