WAEC Past Questions and Answers - Page 4192

20,956.

In the diagram above, PQ and XY are two concentric arc; center O, the ratio of the length of the two arc is 1:3, find the ratio of the areas of the two sectors OPQ and OXY

A.

1:3

B.

1:6

C.

1:9

D.

2:3

E.

4:9

Correct answer is C

Let the radius of the arc PQ = r and the radius of the arc XY = R.

Length of arc PQ = \(\frac{\theta}{360} \times 2\pi r = 1\)

Length of arc XY = \(\frac{\theta}{360} \times 2\pi R = 3\)

Ratio of the arc = \(\frac{r}{R} = \frac{360 \times 2\pi \theta}{2\pi \theta \times 360 \times 3}\)

= \(\frac{1}{3}\)

Ratio of their area = \((\frac{1}{3})^2 = \frac{1}{9}\)

= 1 : 9

20,957.

Find the area of an equivalent triangle of side 16cm

A.

64√3cm2

B.

72√3cm2

C.

96cm2

D.

128√3cm2

E.

128cm2

Correct answer is A

Area = 1/2 x 16 x 16sin60o = 64√3cm2

20,958.

What is the electric potential energy between two protons each of charge q and at a distance of r apart? (Permittivity of free space = εo)

A.

4πεoq2r

B.

qr/4πεo

C.

q/4πεor

D.

q2/4πεor

E.

q2/4πεo

Correct answer is C

No explanation has been provided for this answer.

20,959.

In the diagram above, O is the center of the circle, |SQ| = |QR| and ∠PQR = 68°. Calculate ∠PRS

A.

34o

B.

45o

C.

56o

D.

62o

E.

68o

Correct answer is A

From the figure, < PQR = 68°

\(\therefore\) < QRS = < QSR = \(\frac{180 - 68}{2}\) (base angles of an isos. triangle)

= 56°

\(\therefore\) < PRS = 90° - 56° = 34° (angles in a semi-circle)

20,960.

Calculate the current in the 3Ω resistor shown in
the diagram above.

A.

3.0A

B.

4.0A

C.

4.3A

D.

12.0A

E.

39.0A

Correct answer is B

Total Resistance R = 1/R = 1/R1 + 1/R2 + 1/R3
R = 12/13Ω
V = IR = (12/13) x 13 = 12v
1 across 3Ω = V/R = 12/3 = 4A