WAEC Mathematics Past Questions & Answers - Page 14

66.

Simplify \(\frac{2-18m^2}{1+3m}\)

A.

2[1+3m]

B.

2[1-3m]

C.

2[1-3m\(^2\)]

D.

2[1+3m\(^2\)]

Correct answer is B

\(\frac{2-18m^2}{1+3m}\) =  \(\frac{2[1-9m^2]}{1+3m}\)

\(\frac{2[1-3m][1+3m]}{1+3m}\)

2[1-3m]

67.

The mean of a set of 10 numbers is 56. If the mean of the first nine numbers is 55, find the 10th number.

A.

75

B.

65

C.

55

D.

45

Correct answer is B

10th number must be over 56 (as it increases the average)

55 x 9 = 495 = sum of first 9 numbers

56 x 10 = 560 = sum of all 10 numbers

560 - 495 = 65 = 10th number

68.

Mrs Gabriel is pregnant. The probability that she will give birth to a girl is 1/2 and with  blue eyes is 1/4. What is the probability that she will give birth to a girl with blue eyes? 

A.

1

B.

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

C.

\(\frac{1}{8}\)

D.

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

Correct answer is C

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

Blue eyes = \(\frac{1}{4}\)

probability that she will give birth to a girl with blue eyes: \(\frac{1}{2}\) x \(\frac{1}{4}\)

= \(\frac{1}{8}\)

69.

Find ∠SON

A.

36º

B.

42º

C.

54º

D.

72º

Correct answer is A

The sum of angles in a triangle = 180º

(180 - 108)º = 72º

Isosceles triangle has both two equal sides and two equal angles.

 ∠OSN =  ∠SON = \(\frac{72}{2}\)

= 36º

70.

In the diagram, MNR is a tangent to the circle centre O at N and ∠NOS = 108°. Find ∠OSN

A.

72°

B.

32°

C.

36°

D.

18°

Correct answer is C

The sum of angles in a triangle = 180º

(180 - 108)º = 72º

Isosceles triangle has both two equal sides and two equal angles.

 ∠OSN =  ∠SON = \(\frac{72}{2}\)

= 36º