2006 - WAEC Mathematics Past Questions and Answers - page 2
11
The ratio of boys to girls in a class is 5:3. Find the probability of selecting at random, a girl from the class
A
\(\frac{1}{8}\)
B
\(\frac{1}{3}\)
C
\(\frac{3}{8}\)
D
\(\frac{3}{5}\)
correct option: c
ratio of boys to girls = 5:3
total = 5 + 3 = 8
Pr(girl) = \(\frac{3}{8}\)
Users' Answers & Commentstotal = 5 + 3 = 8
Pr(girl) = \(\frac{3}{8}\)
12
\(\begin{array}{c|c} x & 1 & 4 & p \ \hline y & 0.5 & 1 & 2.5\end{array}\). The table above satisfies the relation y = k\(\sqrt{x}\), where k is a positive constant. Find the value of K.
A
0.5
B
1
C
1.5
D
2
correct option: a
y = k\(\sqrt{x}\) when y = 1, x = 4
k = \(\frac{y}{\sqrt{x}}\)
= \(\frac{1}{\sqrt{4}}\)
= \(\frac{1}{2}\)
= 0.5
Users' Answers & Commentsk = \(\frac{y}{\sqrt{x}}\)
= \(\frac{1}{\sqrt{4}}\)
= \(\frac{1}{2}\)
= 0.5
13
\(\begin{array}{c|c} x & 1 & 4 & p \ \hline y & 0.5 & 1 & 2.5\end{array}\). The table below satisfies the relation y - k\(\sqrt{x}\), where k is a positive constant. Find the value of P,
A
2
B
4
C
10
D
25
correct option: d
From y = \(\frac{1}{2} \sqrt{x}\)
when y = 2.5 or \(\frac{5}{2}\), x = P
\(\frac{5}{2} \times \frac{1}{2} \sqrt{P}\)
\(\sqrt{P} = \frac{10}{2} = 5\)
P = 52
= 25
Users' Answers & Commentswhen y = 2.5 or \(\frac{5}{2}\), x = P
\(\frac{5}{2} \times \frac{1}{2} \sqrt{P}\)
\(\sqrt{P} = \frac{10}{2} = 5\)
P = 52
= 25
14
What must be added to x2 - 3x to make it a perfect square?
A
\(\frac{9}{4}\)
B
\(\frac{9}{2}\)
C
6
D
9
correct option: a
x2 - 3x + k(perfect square)
k = (-\(\frac{3}{2}\))2 ; k = \(\frac{9}{4}\)
Users' Answers & Commentsk = (-\(\frac{3}{2}\))2 ; k = \(\frac{9}{4}\)
15
Given that (2x - 1)(x + 5) = 2x2 - mx - 5, what is the value of m
A
11
B
5
C
-9
D
-10
correct option: c
(2x - 1)(x + 5) = 2x2 - mx - 5
2x2 + 10x - x - 5
= 2x2 + 9x - 5 = 2x2 - mx - 5
comparing the co-efficient of x
-m = 9
m = -9
Users' Answers & Comments2x2 + 10x - x - 5
= 2x2 + 9x - 5 = 2x2 - mx - 5
comparing the co-efficient of x
-m = 9
m = -9
16
What is the place value of 9 in the number 3.0492?
A
\(\frac{9}{10000}\)
B
\(\frac{9}{1000}\)
C
\(\frac{9}{100}\)
D
\(\frac{9}{10}\)
17
If the simple interest on a sum of money invested at 3% per annum for 2\(\frac{1}{2}\) years is N123, find the principal.
A
N676.50
B
N820
C
N1,640
D
N4,920
correct option: c
I = N123; R = 3%' T = 2\(\frac{1}{2}\) yrs; P = \(\frac{100 \times 1}{RT}\)
P = \(\frac{100 \times 123}{3 \times 2.5}\)
principal(P) = N1640
Users' Answers & CommentsP = \(\frac{100 \times 123}{3 \times 2.5}\)
principal(P) = N1640
18
A machine valued at N20,000 depreciates by 10% every year. What will be the value of the machine at the end of two years?
A
N16,200
B
N1,4,200
C
12,000
D
8000.
correct option: a
D = P(I - \(\frac{R}{100}\))n where P = N20,000; R = 10%, n = 2
D = 20,000(I - \(\frac{10}{100}\))2
= 20000(0.9)2
20,000 x 0.81 = N16,200
Users' Answers & CommentsD = 20,000(I - \(\frac{10}{100}\))2
= 20000(0.9)2
20,000 x 0.81 = N16,200
19
If 2x + y = 10, and y \(\neq\) 0, which of the following is not a possible value of x?
A
4
B
5
C
8
D
10
correct option: b
The value for which the equation is impossible
2x = 10 (if y = 0)
x = 5
Users' Answers & Comments2x = 10 (if y = 0)
x = 5
20
If x + y = 12 and 3x - y = 20, find the value of 2x - y
A
8
B
10
C
12
D
15
correct option: c
x + y = 12
+ 3x - y = 20
---------------
4x = 32
x = 8
x + y = 12; 8 + y = 12; y = 12 - 8
= 4
2x - y = 2(8) - 4; 16 - 4 = 12
Users' Answers & Comments+ 3x - y = 20
---------------
4x = 32
x = 8
x + y = 12; 8 + y = 12; y = 12 - 8
= 4
2x - y = 2(8) - 4; 16 - 4 = 12