WAEC Mathematics Past Questions & Answers - Page 99

491.

Given that P = x2 + 4x - 2, Q = 2x - 1 and Q - p = 2, find x

A.

-2

B.

-1

C.

1

D.

2

Correct answer is B

P = x2 + 4x - 2, Q = 2x - 1

Q - p = 2, (2x - 1) - (x2 + 4x - 2) = 2

2x - 1 - x2 - 4x + 2 = 2

-2x - x2 + 1

-x2 - 2x - 1 = 0

x2 + 2x + 1 = 0

x2 + x + x + 1 = 0

x(x + 1) + 1(x + 1) = 0

(x + 1)(x + 1) = 0

x + 1 = 0 or x + 1 = 0

x = -1 or x = -1

x = -1

492.

An interior angle of a regular polygon is 5 times each exterior angle. How many sides has the polygon?

A.

15

B.

12

C.

9

D.

6

Correct answer is B

Let the interior angle = xo

interior angle = 5xo (sum of int. angle ann exterior)

(angles = angle or straight line)

6x = 180

x = \(\frac{180}{6}\)

x = 30o

no. of sides = \(\frac{\text{sum of exterior angles}}{\text{exterior angle}}\)

= \(\frac{360}{30}\) = 12

493.

Express \(\frac{2}{x + 3} - \frac{1}{x - 2}\) as a simple fraction

A.

\(\frac{x - 7}{x^2 + x - 6}\)

B.

\(\frac{x - 1}{x^2 + x - 6}\)

C.

\(\frac{x - 2}{x^2 + x - 6}\)

D.

\(\frac{x - 27}{x^2 + x - 6}\)

Correct answer is A

\(\frac{2}{x + 3} - \frac{1}{x - 2}\) = \(\frac{2(x - 2) - (x - 3)}{(x + 3) (x - 2)}\)

= \(\frac{2x - 4 - x - 3}{x^2 - 2x + 3x - 6}\)

= \(\frac{x -7}{x^2 + x - 6}\)

= \(\frac{x - 7}{x^2 + x - 6}\)

494.

When a number is subtracted from 2, the result equals 4 less than one-fifth of the number. Find the number

A.

11

B.

\(\frac{15}{2}\)

C.

5

D.

\(\frac{5}{2}\)

Correct answer is C

Let the number be y, subtract y from 2 i.e 2 - y

2 - y = 4 < \(\frac{1}{5}\) y,

2 - y = \(\frac{y}{5}\) - 4

2 - y + 4 = \(\frac{y}{5}\)

6 =  \(\frac{y}{5}\) + y

6 =  \(\frac{y + 5y}{5}\)

6 =  \(\frac{6y}{5}\) 

multiplying through by 5
6 * 5 = 6y

\(\frac{30}{6}\) = y

= 5

495.

What is the locus of the point X which moves relative to two fixed points P and M on a plane such that < PXM = 30o

A.

the bisector of the straight line joining P and M

B.

an arc of a circle with PM as a chord

C.

the bisector of angle PXM

D.

a circle centre X and radius PM

Correct answer is B

No explanation has been provided for this answer.