2008 - WAEC Mathematics Past Questions and Answers - page 1
1
If x% of 240 equals 12, find x
A
x = 1
B
x = 3
C
x = 5
D
x = 7
correct option: c
x% of 240 = 12
\(\frac{x}{100} \times 240 = 12\)
x = \(\frac{12 \times 100}{240}\)
x = 5
Users' Answers & Comments\(\frac{x}{100} \times 240 = 12\)
x = \(\frac{12 \times 100}{240}\)
x = 5
2
Evaluate \(\frac{(3.2)^2 - (4.8)^2}{3.2 + 1.8}\)
A
-0.08
B
-1.60
C
-10.24
D
-12.80
correct option: b
\(\frac{(3.2)^2 - (4.8)^2}{3.2 + 1.8} = \frac{(3.2 - 4.8)(3.2 + 4.8)}{(3.2 + 4.8)}\)
= 3.2 - 4.8
= -1.60
Users' Answers & Comments= 3.2 - 4.8
= -1.60
3
Simplify \(\sqrt{50} + \frac{10}{\sqrt{2}}\)
A
10
B
10\(\sqrt{2}\)
C
20
D
20\(\sqrt{2}\)
correct option: b
\(\sqrt{50} + \frac{10}}{\sqrt{2}} = \(\frac{\sqrt{50}}{1} + \sqrt{10}{\sqrt{2}}\)
= \(\frac{\sqrt{50 \times 2} + 10}{\sqrt{2}}\)
= \(\frac{\sqrt{100} + 10}{\sqrt{2}}\)
= \(\frac{10 + 10}{\sqrt{2} = \frac{20}{\sqrt{2}}\)
= \(\frac{20}{\sqrt{2}}\) \times \frac{\sqrt{2}}{\sqrt{2}}\)
= \(\frac{20\sqrt{2}}{2}\)
= 10\(\sqrt{2}\)
Users' Answers & Comments= \(\frac{\sqrt{50 \times 2} + 10}{\sqrt{2}}\)
= \(\frac{\sqrt{100} + 10}{\sqrt{2}}\)
= \(\frac{10 + 10}{\sqrt{2} = \frac{20}{\sqrt{2}}\)
= \(\frac{20}{\sqrt{2}}\) \times \frac{\sqrt{2}}{\sqrt{2}}\)
= \(\frac{20\sqrt{2}}{2}\)
= 10\(\sqrt{2}\)
4
P naira invested for 4 years invested for 4 years at r% simple interest per annum yields 0.36 p naira interest. Find the value of r
A
1\(\frac{1}{9}\)
B
1\(\frac{4}{9}\)
C
9
D
11
correct option: c
I = \(\frac{PRT}{100}\)
where r = r% p.a; I = 0.36p
0.36p = \(\frac{P \times r \times 4}{100}\)
\(\frac{0.36 \times 100}{4}\) = r
r = 9
Users' Answers & Commentswhere r = r% p.a; I = 0.36p
0.36p = \(\frac{P \times r \times 4}{100}\)
\(\frac{0.36 \times 100}{4}\) = r
r = 9
5
A trader bought 100 tubers at 5 for N350.00. She sold them in sets of 4 for N290.00. Find her gain percent.
A
3.6%
B
3.5%
C
3.5%
D
2.55
correct option: a
Cost price, c.p = \(\frac{100}{5}\) x N350 = N7000
Selling price, s.p = \(\frac{100}{5}\) x N290 = N7250
%Gain = \(\frac{S.p - C.p}{C.p}\) x 100%
= \(\frac{7250 - 7000}{7000}\) x 100% = \(\frac{250 \times 100}{7000}\)
= 3.6% (approx.)
Users' Answers & CommentsSelling price, s.p = \(\frac{100}{5}\) x N290 = N7250
%Gain = \(\frac{S.p - C.p}{C.p}\) x 100%
= \(\frac{7250 - 7000}{7000}\) x 100% = \(\frac{250 \times 100}{7000}\)
= 3.6% (approx.)
6
If p-2g + 1 = g + 3p and p - 2 = 0, find g
A
-2
B
-1
C
1
D
2
correct option: b
p - 2g + 1 = g + 3p.........(1)
p - 2 = 0 .........(2)
From (2), p = 2; put p = 2 into (1);
2 - 2g + 1 = g + 3(2)
3 - 2g = g + 6
-2g - g = 6 - 3
-3g = 3
g = \(\frac{3}{-3}\)
g = -1
Users' Answers & Commentsp - 2 = 0 .........(2)
From (2), p = 2; put p = 2 into (1);
2 - 2g + 1 = g + 3(2)
3 - 2g = g + 6
-2g - g = 6 - 3
-3g = 3
g = \(\frac{3}{-3}\)
g = -1
7
Simplify \(\frac{\frac{1}{x} + \frac{1}{y}}{x + y}\)
A
\(\frac{1}{x + y}\)
B
\(\frac{1}{xy}\)
C
x + y
D
xy
correct option: b
\(\frac{\frac{1}{x} + \frac{1}{y}}{x + y}\) = \(\frac{\frac{y + x}{xy}}{x + y}\)
= \(\frac{x + y}{xy}\)
= \(\frac{x + y}{xy} \times \frac{1}{x + y}\)
= \(\frac{1}{xy}\)
Users' Answers & Comments= \(\frac{x + y}{xy}\)
= \(\frac{x + y}{xy} \times \frac{1}{x + y}\)
= \(\frac{1}{xy}\)
8
Simplify 3\(\sqrt{27x^3y^9}\)
A
9xy3
B
3xy6
C
3xy3
D
9y3
correct option: c
3\(\sqrt{27x^3y^9}\) = 3\(\sqrt{27} \times 3\sqrt{3^3} \times 3\sqrt{y^9}\)
= 3 \(\times x \times y^3\)
= 3xy3
Users' Answers & Comments= 3 \(\times x \times y^3\)
= 3xy3
9
Given that x = 2 and y = -\(\frac{1}{4}\), evaluate \(\frac{x^2y - 2xy}{5}\)
A
zero
B
\(\frac{1}{5}\)
C
1
D
2
correct option: a
Given; x = 2; y = \(\frac{-1}{4}\)
= \(\frac{x^2y - 2xy}{5}\)
= \(\frac{2^2(\frac{-1}{4}) - 2(2)(\frac{-1}{4})}{5}\)
= \(\frac{4(\frac{-1}{4}) + 4(\frac{-1}{4})}{5}\)
= \(\frac{1 + 1}{5}\)
= \(\frac{0}{5}\)
= 0
Users' Answers & Comments= \(\frac{x^2y - 2xy}{5}\)
= \(\frac{2^2(\frac{-1}{4}) - 2(2)(\frac{-1}{4})}{5}\)
= \(\frac{4(\frac{-1}{4}) + 4(\frac{-1}{4})}{5}\)
= \(\frac{1 + 1}{5}\)
= \(\frac{0}{5}\)
= 0
10
Factorize 5y2 + 2ay - 3a2
A
(a - y)(5y - 3a)
B
(y - a)(5y - 3a)
C
(y - a)(5y + 3a)
D
(y + a)(5y 3a)
correct option: d
5y2 + 2ay - 3a2 = 5y2 + 5ay - 3a2
= 5y(y + a) - 3a(y + a)
= (y + a)(5y - 3a)
Users' Answers & Comments= 5y(y + a) - 3a(y + a)
= (y + a)(5y - 3a)