# 1998 - WAEC Mathematics Past Questions & Answers - page 1

1

Find the root of the equation 2x$$^2$$ - 3x - 2 = 0

A
x = -2 or 1/2
B
x = -2 or1
C
x = -2 or 2
D
x = -1 or 2
CORRECT OPTION: e

2x$$^2$$ - 3x - 2 = 0

2x$$^2$$ - 4x + x - 2 = 0

2x(x - 2) + 1(x - 2) = 0

(2x + 1)(x - 2) = 0

x = $$\frac{-1}{2}$$ or x = 2

2

What value of k makes the given expression a perfect square ? m$$^2$$ - 8m + k = 0

A
2
B
4
C
8
D
16
CORRECT OPTION: d

Take half the coefficient of m and square it
=> (-8/2)2 = k = 16

3

If log$$_{10}$$ q = 2.7078, what is q?

A
5102
B
849.9
C
510.2
D
84.99
CORRECT OPTION: c

q = 10$$^{2.7078}$$

Antilog of 2.7078 = 510.2

4

Cos x is negative and sin x is negative.Which of the following is true of x?

A
0o < x < 90o
B
90o < x <180o
C
180o < x < 270o
D
270o < x <360o
CORRECT OPTION: c

In the 3rd quadrant, only the tan of angles are positive.

The 3rd quadrant = 180° < x < 270°

5

Simplify 0.63954 ÷ 0.003 giving your answer correct to two significant figures

A
213.18
B
213.00
C
213
D
210
CORRECT OPTION: d

= $$\frac{0.63954}{0.003}$$

moving the decimal places, we have

= $$\frac{639.54}{3}$$

= 213.18

$$\approxeq$$ 210 (to 2 s.f.)

6

If log$$_{10}$$ a = 4; what is a?

A
0.4
B
40
C
400
D
1000
CORRECT OPTION: e

log$$_{10}$$ a = 4

a = 10$$^4$$

= 10000

7

A student measured the length of a room and obtained the measurement of 3.99m. If the percentage error of is measurement was 5% and his own measurement was smaller than the length , what is the length of the room?

A
3.78m
B
3.80m
C
4.18m
D
4.20m
CORRECT OPTION: d

Let the actual length of the room = y m

$$\therefore \frac{y - 3.99}{y} \times 100% = 5%$$

$$100(y - 3.99) = 5y \implies 100y - 399 = 5y$$

$$100y - 5y = 399 \implies y = \frac{399}{95}$$

y = 4.2 m

8

When an aeroplane is 800m above the ground, its angle of elevation from a point P on the ground is 30o. How far is the plane from P by line of sight?

A
400m
B
800m
C
1500m
D
1600m
CORRECT OPTION: d

From the diagram, $$\sin 30 = \frac{800}{x}$$

$$x = \frac{800}{\sin 30}$$

= $$\frac{800}{0.5}$$

= 1600 m

9

Convert 35 to a number in base two

A
1011two
B
10011two
C
100011two
D
110010two
CORRECT OPTION: c

10
The nth term of a sequence is represented by 3 x 2(2-n). Write down the first three terms of the sequence
A
3/2, 3, 6
B
6, 3, 3/2
C
3/2, 3, 1/3
D
2/3, 3, 8/3
CORRECT OPTION: b
When n = 1, n = 2, n = 3
3 x 22 - 1 = 6
3 x 22 - 2 = 3
3 x 22 - 3 = 3/2
Pages: