WAEC Mathematics Past Questions & Answers - Page 174

866.

Ladi sold a car for N84,000 at a loss of 4%. How much did ladi buy the car?

A.

80,500

B.

80,640

C.

87,360

D.

87,500

Correct answer is C

p>The car was sold at 96% ---- N84,000.00
The price of the car is 100% ---- ?
\(\frac{4}{100} \times \frac{84,000}{1}\);

 

= 3360

Car's price = 3360 + 84000

= 87360

867.

If \(y \alpha \frac{1}{x^2}\) and \(y = 1\frac{1}{4}\) when x = 4, find the value of y when \(x = \frac{1}{2}\)

A.

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

B.

5

C.

10

D.

80

Correct answer is D

\(y \propto \frac{1}{x^2} \Rightarrow y = \frac{k}{x^2} \Rightarrow k = yx^2\\
k = 1\frac{1}{4} \times 4^2 \Rightarrow k=\frac{5}{4}\times \frac{16}{1}=20\\
∴y = 20 \div \left(\frac{1}{2}\right)^2=20\times \frac{4}{1}=80\)

868.

A rectangular packet has inner dimension 16cm by 12cm by 6cm. How many cubes of sugar of side 2cm can be neatly packed into the packet?

A.

90

B.

144

C.

150

D.

288

Correct answer is B

Volume of rectangular packet = (16 x 12 x 6)cm3 = 1152cm3. Volume of cube of sugar = 2 x 2 x 2 = 8cm
∴ The number of cubes f sugar \(=\frac{1152}{8}=144\)

869.

XOY is a real sector of a circle center O of radius 3.5cm which subtends an angle of 144o at the center. Calculate, in term of ϖ, the area of the sector

A.

1.4ϖcm2

B.

2.8ϖcm2

C.

4.9ϖcm2

D.

9.8ϖcm2

Correct answer is C

Area of a sector \(=\frac{\theta}{360}\times \pi r^2\\
\left(\frac{144}{360}\times \pi \times \frac{3.5}{1} \times 3.5\right)cm^2 = 4.9\pi cm^2\)

870.

The angle of elevation of the top of a cliff 15 meters high from a landmark is 60°. How far is the landmark from the foot of the cliff? Leave your answer in surd form

A.

\(15\sqrt{3}m\)

B.

\(15\sqrt{2}m\)

C.

\(10\sqrt{3}m\)

D.

\(5\sqrt{3}m\)

Correct answer is A

Tan 60º = \(\frac{15}{x}\)

cross multiply:

x = \(\frac{15}{\sqrt3}\) = 5\(\sqrt3\)m