WAEC Mathematics Past Questions & Answers - Page 198

986.

A ladder, 6m long, leans against a vertical wall at an angle 53o to the horizontal. How high up the wall does the ladder reach?

A.

3.611m

B.

4.521m

C.

4.792m

D.

7.962m

Correct answer is C

Sin 53 = \(\frac {h}{6} \)
h = 6 sin 53 = 6 x 0.7986
= 4.792m

987.

Given, that \(4P4_5 = 119_{10}\), find the value of P

A.

1

B.

2

C.

3

D.

4

Correct answer is C

\(4P4_5 = 119_{10}\)

\(4 \times 5^2 + P \times 5^1 + 4 \times 5^0 = 119\)

\(100 + 5P + 4 = 119\)

\(5P = 119 - 104 = 15\)

\(P = 3\)

988.

In\( ∆ PQR, P\hat{Q}P = 84^°, |Q\hat{P}R |= 43^°\) and |PQ| = 5cm. Find /QR/ in cm, correct to 1 decimal place.

A.

3.4

B.

4.3

C.

5.9

D.

6.2

Correct answer is B

Using the sine rule
\(\frac{|QR|}{sinP}=\frac{|PQ|}{sinR}\\
\frac{x}{sin43^o}=\frac{5}{sin53^o}\\
x = \frac{5\times sin43^o}{sin53^o}\\
=\frac{5\times 0.6820}{0.7986}\\
=4.3\)

989.

Find the value of x in the equation 3x\(^2\) - 8x - 3 = 0

A.

\(\frac{1}{3},-3\)

B.

\(-\frac{1}{3},-3\)

C.

\(-\frac{1}{3},3\)

D.

\(\frac{1}{3},3\)

Correct answer is C

3x\(^2\) - 8x - 3 = 0

3x\(^2\) - 9x + x - 3 = 0

3x(x - 3) + 1(x - 3) = 0

(3x + 1)(x - 3) = 0

3x = -1 \(\implies\) x = \(-\frac{1}{3}\)

or x = 3.

990.

In the diagram, ZM is a straight line. Calculate the value of x.

A.

27o

B.

30o

C.

35o

D.

37o

Correct answer is C

The sum of angles in a triangle is 180o
2xo + (2x -21)o + ∠ZYP = 180o
Also ∠ZYP = 180o - (3x+14)o
∴2xo + (2x-21)o + 180o - (3x+14)o = 180
x = 35o