WAEC Mathematics Past Questions & Answers - Page 190

946.

If \(\left(\frac{1}{4}\right)^{(2-y)} = 1\), find y.

A.

-2

B.

\(-\frac{1}{2}\).

C.

\(\frac{1}{2}\)

D.

2

Correct answer is D

\(2^{-2(2-y)}-x=2^{0}; -4 + 2y = 0\\
2y = 4; y = 2\)

947.

In the diagram, POQ is the diameter of the circle centre O. Calculate ∠QRS

A.

35o

B.

70o

C.

100o

D.

125o

Correct answer is A

∠PSQ = 90° (angle in a semi-circle)
(when SR is joined to SP)
∠SPQ = 180 – (90+35) = 180 – 125 = 55°
∠QRS + ∠SPQ = 180° (opposite angles in a cyclic quad is supplementary)
∠QRS = 180° - 55°
= 125°

948.

Given that x + y = 7 and 3x-y = 5, evaluate \(\frac{y}{2}-3\).

A.

-1

B.

1

C.

3

D.

4

Correct answer is A

\(x + y = 7 ------ I\\
3x – y = 5 ------ II\)
Add I and II;
\(4x = 12 => x = \frac{12}{4} = 3\\
Y = 7 – 3 = 4, evaluate \hspace{1mm} \frac{y}{2} – 3\\
\frac{4}{2} – 3 => 2-3 = -1\)

949.

Find the area of a rectangle of length 4cm and whose diagonal is 8cm, (Leave your answer in surd form)

A.

8√3cm2

B.

12√3cm2

C.

16√2cm2

D.

16√3cm2

Correct answer is D

|AB| = 4cm
|BC| = 8cm
In right-angled BAC;

8\(^2\) = 4\(^2\) + |AC|\(^2\)

|AC|\(^2\) = 8\(^2\) - 4\(^2\)

|AC\\(^2\) = 64 - 16 → 48

|AC| = \(\sqrt{48}\)cm → \(4\sqrt{3}cm\)

The area of rectangle = L x B

= |AB| x |AC|
= \((4 \times 4\sqrt{3}cm^2\)
=\(16\sqrt{3}cm^2\)

950.

The angle of elevation of the top of a tower from a point on the ground which is 36m away from the foot of the tower is 30o. Calculate the height of the tower.

A.

62.35m

B.

20.78m

C.

18.00m

D.

10.39m

Correct answer is B

Where H is the height of the tower H = ?
\(Tan 30^{\circ} = \frac{H}{36} \Rightarrow H = 36 \times tan30^{\circ}\\
H = 36 \times 0.5774 = 20.79\)