WAEC Mathematics Past Questions & Answers - Page 123

611.

The diagram shows a rectangular cardboard from which a semi-circle is cut off. Calculate the area of the remaining part

A.

44cm2

B.

99cm2

C.

154cm2

D.

165cm2

Correct answer is B

Area of remaining = Area of rectangle = Area of semi-circle

22 x 8 - \(\frac{1}{2}\)xar2

ehere r - \(\frac{14}{2}\)cm = 7cm

Area of remaining = 176 - \(\frac{1}{2}\) x \(\frac{22}{4}\) x 7 x 7

= 176 - 77

= 99cm2

612.

The diagram is a net right rectangular pyramid. Calculate the total surface area

A.

208cm2

B.

112cm2

C.

92cm2

D.

76cm2

Correct answer is C

Total surface area = sum of the area of the \(\bigtriangleup\) S + Area of the rectangle

= 2 x Area of \(\bigtriangleup\) PTQ + 2 x Area of \(\bigtriangleup\) QUR + Area of rectangle PQRS

2 x \(\frac{1}{2}\)(8 x 4) + 2 x \(\frac{1}{2}\)(5 x 4) + 8 x 5

= 32 + 20 + 40

= 92cm2

613.

In the diagram, GI is a tangent to the circle at H. If EF//GI, calculate the size of < EHF

A.

126o

B.

72o

C.

64cmo

D.

32cmo

Correct answer is B

F = 54o (Alternate triangle angles)

< GHE = F = 54o(Angle between a chord and a tangent = angles in the alternate segment)

Now, < GHE + < EHF + < IHF = 180o(Angles on a straight line)

54o + < EHF + 54o = 180o

< EHF = 180o - 108o

= 72o

614.

The shaded portion in the diagram is the solution of

A.

x + y \(\leq\) 3

B.

x + y < 3

C.

x + y > 3

D.

x + y \(\geq\) 3

Correct answer is B

Using \(\frac{x}{a} + \frac{y}{b}\) < 1for the equation of the time

where a = intercept on x-axis and b = intercept on y - axis

\(\frac{x}{3} + \frac{y}{3} = 1\)

= \(\frac{x + y}{3} = 1\)

= x + y < 3

615.

In the diagram, O is the centre of the circle, < SQR = 60o, < SPR = y and < SOR = 3x. Find the value of (x + y)

A.

110o

B.

100o

C.

80o

D.

70o

Correct answer is B

3x = 2 x 60 = 2y (Angle at centre = 2 x angle at circumference)

3x = 2 x 60

x = \(\frac{2 \times 60}{3}\) = 40o

2 x 60 = 2y

y = 60o

x + y = 40 + 60

= 100o