WAEC Mathematics Past Questions & Answers - Page 117

581.

In a quiz competition, a student answers n questions correctly and was given D(n + 50) for each question correctly answered. If he gets D600.00 altogether, how many questions did he answer correctly?

A.

18

B.

15

C.

12

D.

10

Correct answer is D

let the number of question = n

n(n + 50) = 600

n2 + 50n - 600 - 0 by quadratic formular

x = \(\frac{b \pm \sqrt{b^2 - 4ac}}{2}\)

n = \(\frac{-50 \pm \sqrt{50^2 - 4(1) (-600)}}{2(1)}\)

= \(\frac{-50 \pm \sqrt{4900}}{2}\)

= \(\frac{-50 + 70}{2}\)

= \(\frac{20}{2}\)

= 10

582.

John pours 96 litres of red oil into a rectangular container with length 220cm and breadth 40cm. Calculate, correct to the nearest cm, the height of the oil in the container

A.

11cm

B.

18cm

C.

21cm

D.

34cm

Correct answer is A

volume of rectangular container = L x B x H

1 litre = 1000cm3

96 litres = \(\frac{1000cm^3}{1 litres}\) x 96 litres

volume = 96000cm3

96000 = 220 x 40 

96--- = 8800H

H = \(\frac{96000}{8800}\)

= 10.97cm

= 11cm

583.

A rectangular garden measures 18.6m by 12.5m. Calculate, correct to three significant figures, the area of the garden

A.

230m2

B.

231m2

C.

232m2

D.

233m2

Correct answer is D

A = L x B

= (18.6 x 12.5)m2

= 232.5m2

= 233m2

584.

The perpendicular bisectors of the sides of an acute-angled triangle are drawn. Which of these statements is correct? They intersect

A.

on one of the vertices

B.

at a midpoint of a side

C.

inside the triangle

D.

outside the triangle

Correct answer is C

No explanation has been provided for this answer.

585.

Find the smaller value of x that satisfies the equation x2 + 7x + 10 = 0

A.

-5

B.

-2

C.

2

D.

5

Correct answer is A

x2 + 7x + 10 = 0

x2 + 5x + 2x + 10 = 0

x(x + 5) + 2(x + 5) = 0

(x + 2)(x + 5) = 0

x + 2 = 0 or x + 5 = 0

x = -2 or x = -5

the smaller value x = -5x2 + 7x + 10 = 0

x2 + 5x + 2x + 10 = 0

x(x + 5) + 2(x + 5) = 0

(x + 2)(x + 5) = 0

x + 2 = 0 or x + 5 = 0

x = -2 or x = -5

the smaller value x = -5