WAEC Mathematics Past Questions & Answers - Page 81

401.

In the diagram, PTR is a tangent to the centre O. If angles TON = 108°, Calculate the size of angle PTN

A.

132o

B.

126o

C.

108o

D.

102o

Correct answer is B

In the diagram; 108° + x + x = 180° (sum of angle in a triangle)

108° + 2x = 180°

x = 180° - 108°

= 72°

x = \(\frac{72^o}{2}\)

= 36°

(Angle between tangent and a chord through the point of contact)

Hence, angle PTN = 90 + 36

= 126°

402.

In the diagram, O is the centre. If PQ//RS and ∠ONS = 140°, find the size of ∠POM.

A.

40o

B.

50o

C.

60o

D.

80o

Correct answer is A

In the diagram above,

∠MNO = 140° and angles on a straight line is 180°

: ∠NMO = (180 - 140)° = 40°

Hence; ∠POM = 40° ( alternate angle ∠S)

403.

The dimension of a rectangular tank are 2m by 7m by 11m. If its volume is equal to that of a cylindrical tank of height 4cm, calculate the base radius of the cylindrical tank. [Take \(\pi = \frac{22}{7}\)]

A.

14cm

B.

7m

C.

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

D.

1\(\frac{3}{4}\)m

Correct answer is C

Volume of rectangular tank = L x B x H

= 2 x 7 x 11

= 154cm3

volume of cylindrical tank = \(\pi r^2h\)

154 = \(\frac{22}{7} \times r^2 \times 4\)

r2 = \(\frac{154 \times 7}{22 \times 4}\)

= \(\frac{49}{4}\)

r = \(\sqrt{\frac{49}{4}} = \frac{7}{2}\)

= 3\(\frac{1}{2}\)m

404.

The volume of a cone of height 3cm is 38\(\frac{1}{2}\)cm3. Find the radius of its base. [Take \(\pi = \frac{22}{7}\)]

A.

3.0cm

B.

3.5cm

C.

4.0cm

D.

4.5cm

Correct answer is B

Using V = \(\frac{3}{1} \pi r^2h\),

so, 38\(\frac{1}{2} = \frac{1}{3} \times \frac{22}{7} \times r^2 \times 3\)

\(\frac{77}{2} = \frac{22}{7} \times r^2\)

r2 = \(\frac{77 \times 7}{2 \times 22}\)

r2 = \(\frac{49}{4}\)

Hence, r = \(\sqrt{\frac{49}{4}}\)

= 3\(\frac{1}{2}\)

405.

Ada draws the graph of y = x2 - x - 2 and y = 2x - 1 on the same axes. Which of these equations is she solving?

A.

x2 - x - 3 = 0

B.

x2 - 3x - 1 = 0

C.

x2 - 3x - 3 = 0

D.

x2 + 3x - 1 = 0

Correct answer is B

Given; y = x2 - x - 2, y = 2x - 1

Using y = y, gives

x2 - x - 2 = 2x - 1

x2 - 3x - 2 + 1 = 0

therefore, x2 - 3x - 1 = 0