WAEC Mathematics Past Questions & Answers - Page 143

711.

In the diagram, O is the centre of the circle and PQRS is a cyclic quadrilateral. Find the value of x.

A.

25o

B.

65o

C.

115o

D.

130o

Correct answer is B

x = 65o (An interior angle of a cyclic quadrilateral = opposite exterior angle).

712.

In the figure /PX/ = /XQ/, PQ//YZ and XV//QR. What is the ratio of the area of XYZQ to te area of \(\bigtriangleup\)YZR?

A.

1:2

B.

2:1

C.

1:2

D.

3:1

Correct answer is B

From the diagram, XYZQ is a parallelogram. Thus, |YZ| = |XQ| = |PX|; \(\bigtriangleup\)PXY, Let the area of XYZQ = A1, the area of \(\bigtriangleup\)PXY

= Area of \(\bigtriangleup\)YZR = A2

Area of \(\bigtriangleup\)PQR = A = A1 + 2A2

But from similarity of triangles

\(\frac{\text{Area of PQR}}{\text{Area of PXY}} = (\frac{PQ}{PX})^2 = (\frac{QR}{XY})^2\)

\(\frac{A}{A_2} = (\frac{2}{1})^2 = \frac{2}{1}\)

A = 4A2 But, A = A1 + 2A

A1 = 4A2 - 2A2

A1 = 2A2

\(\frac{A_1}{A_2}\) = 2

A1:A2 = 2:1


Area of XYZQ:Area of \(\bigtriangleup\)YZR = 2:1

713.

In the diagram, PQ//RS, QU//PT and < PSR = 42o. Find angle x.

A.

84o

B.

48o

C.

42o

D.

32o

Correct answer is C

From the diagram, < QPS = xo (Corresponding angles)

Also, < QPS = < PSR(Alternate angles)

x = 42o

714.

In the figure shown, PQs is a straight line. What is the value of < PRQ?

A.

128o

B.

108o

C.

98o

D.

78o

Correct answer is D

< QPR + < PRQ = < RQS

(Sum of two interior angles of a triangle = Opposite exterior angles)

70o + < PRQ = 148

< PRQ = 148o - 70o

= 78o

715.

In the diagram above, PQRS is a rhombus. /PR/ = 10cm and /QS/ = 24cm. Calculate the perimeter of the rhombus.

A.

34cm

B.

52cm

C.

56cm

D.

96cm

Correct answer is B

For a rhombus, all the sides are equal and diagonals bisect each other at 90o. Hence, the triangles formed are congruent: (under RHS).

Thus: \(\bar{PS}^2\) = 52 + 122

\(\bar{PS} = \sqrt{25 + 144}\)

= \(\sqrt{169}\)

\(\bar{PS}\) = 13cm

perimeter = 4 x length of a side

= 4 x 13cm

= 52cm