WAEC Mathematics Past Questions & Answers - Page 282

1,406.
1,407.

A cuboid of base 12.5cm by 20cm holds exactly 1 litre of water. What is the height of the cuboid? (1 litre =1000cm3)

A.

2cm

B.

4cm

C.

5cm

D.

8cm

E.

10cm

Correct answer is B

Volume of cuboid = length x breadth x height 12.5 x 20 x h = 1000 250h = 1000 h = 4 cm

1,408.

The angle subtended at the centre by a chord of a circle radius 6cm is 120°. Find the length of the chord.

A.

3cm

B.

6cm

C.

\(4\sqrt{2}\) cm

D.

\(3\sqrt{3}\) cm

E.

\(6\sqrt{3}\) cm

Correct answer is E

\(\frac{r}{6} = \sin 60 \)

\(r = 6 \sin 60\)

= \(6 \times \frac{\sqrt{3}}{2}\)

= \(3\sqrt{3}\)

Chord = 2r = \( 2 \times 3\sqrt{3}\)

= \(6\sqrt{3}\)

1,409.

Solve the equation log8x - 4log8x = 2

A.

1/4

B.

1/2

C.

1

D.

2

E.

4

Correct answer is A

log8x - 4log8x = 2; log8x - log8x4 = 2
log8x/x4 = 2
x/x4 = 82 = 1/x3 = 64
x3 = (1/4)3; x = 1/4

1,410.

Factorise: 6x\(^2\) + 7xy - 5y\(^2\)

A.

(6x + 5y)(x - y)

B.

(2x + 5y)(3x - y)

C.

(3x + y)(2x - 5y)

D.

(3x + 5y)(2x - y)

E.

(2x + y)(3x - 5y)

Correct answer is D

\(6x^2 + 7xy - 5y^2\)

= \(6x^2 + 10xy - 3xy - 5y^2\)

= \(2x(3x + 5y) - y(3x + 5y)\)

= \((2x - y)(3x + 5y)\)