WAEC Mathematics Past Questions & Answers - Page 22

106.

Height(cm) 160 161 162 163 164

165

No. of players 4 6 3 7 8 9

the table shows the height of 37 players of a basketball team calculates correct to one decimal place the mean height of the players.

A.

163.0

B.

162.0

C.

160.0

D.

165.0

Correct answer is A

∑fx = (160 * 4) + (161 * 6) + (162 * 3) + (163 * 7) + (164 * 8) + (165 * 9)  

=640 + 966 + 486 + 1,141 + 1,312 + 1,485

= 6,030

∑f = 4 + 6 + 3 + 7 + 8 + 9

= 37

= \(\frac{∑fx}{∑f}\)

= \(\frac{6030}{37}\)

= 162.97 or 163

107.

In the diagram, line \(\overline{EC}\) is a diameter of the circle ABCDE.

If angle ABC equals 158°, find ∠ADE

A.

112

B.

90

C.

68

D.

22

Correct answer is C

No explanation has been provided for this answer.

108.

Given that sin x = 3/5, 0 ≤ x ≤ 90, evaluate (tanx + 2cosx)

A.

2\(\frac{11}{20}\)

B.

\(\frac{11}{20}\)

C.

2\(\frac{7}{20}\)

D.

\(\frac{1}{20}\)

Correct answer is B

Sin x = \(\frac{opp}{hyp}\)

sinx = \(\frac{3}{5}\)

using Pythagoras' theorem

 hyp\(^2\) = opp\(^2\) + adj\(^2\)

adj\(^2\) = 5\(^2\) - 3\(^2\) = 25 - 9

adj\(^2\) = 16 

adj =  16 

adj = 4.

tanx = \(\frac{opp}{adj}\)

= \(\frac{3}{4}\)

cosx = \(\frac{adj}{hyp}\)

= \(\frac{4}{5}\)

(tanx + 2cosx) = \(\frac{3}{4}\) + 2(\(\frac{4}{5}\))

= \(\frac{15 + 32}{20}\)

= \(\frac{47}{20}\) or 

2 \(\frac{7}{20}\)

109.

A cone has a base radius of 8cm and height 11cm. calculate , correct to 2d.p, the curved surface area

A.

341.98cm\(^2\)

B.

276.57cm\(^2\)

C.

201.14cm\(^2\)

D.

477.71cm\(^2\)

Correct answer is A

Where l\(^2\) = h\(^2\) + r\(^2\)

l\(^2\) = 11\(^2\) + 8\(^2\)

l = √185

l = 13.60cm

The formula of CSA of Cone is πrl

\(\frac{22}{7}\) * 8 * 13.60

= 341.979 or 341.98 (2d.p)

110.

In the diagram, PQRS is a circle. find the value of x.

A.

50°

B.

30°

C.

80°

D.

100°

Correct answer is A

Opp. angles in a cyclic quadrilateral always add up to 180°

∠P + ∠R & ∠Q + ∠S = 180

x + x+y = 180 

2x + y = 180... i

2y - 30 + x = 180 

2y + x = 180 + 30

x + 2y = 210 ... ii

Elimination method:

(2x + y = 180) * 1 --> 2x + y = 180

(x + 2y = 210) * 2 --> 2x + 4y = 420

Subtracting both equations

- 3y = - 240

y = 80°

using eqn i

2x + y = 180

2x + 80 = 180

2x = 100

x = 50°