WAEC Mathematics Past Questions & Answers - Page 34

166.

A solid cuboid has a length of 7 cm, a width of 5 cm, and a height of 4 cm. Calculate its total surface area.

A.

280 cm\(^2\)

B.

166 cm\(^2\)

C.

140 cm\(^2\)

D.

83 cm\(^2\)

Correct answer is B

Total = 2(LB + BH + LH) 

Surface area 

= 2(7 x 5 + 5 x 4 + 7 x 4)

= 2(35 + 20 + 28)

= 2(83) 

= 166cm\(^2\) 

167.

Two buses start from the same station at 9.00am and travel in opposite directions along the same straight road. The first bus travel at a speed of 72 km/h and the second at 48 km/h. At what time will they be 240km apart?

A.

1:00 pm

B.

12:00 noon

C.

11:00 am

D.

10:00 am

Correct answer is C

Let x be the time 

Then 72x + 48x = 240 

\(\frac{120}{120} \times \frac{240}{120}\)

x = 2hrs

9:00 + 2hrs = 11:00 am 

168.

Given that x is directly proportional to y and inversely proportional to Z, x = 15 when y = 10 and Z = 4, find the equation connecting x, y and z

A.

x = \(\frac{6y}{z}\)

B.

x = \(\frac{12y}{z}\)

C.

x = \(\frac{3y}{z}\)

D.

x = \(\frac{3y}{2z}\)

Correct answer is A

\(x\) x \(\frac{y}{z}\) 

x = \(\frac{ky}{z}\)

15 = \(\frac{10k}{4}\) 

 \(\frac{60}{10}\) = k = 6

Therefore; x = \(\frac{6y}{z}\)

169.

Find the quadratic equation whose roots are \(\frac{1}{2}\)  and -\(\frac{1}{3}\) 

A.

3x\(^2\) + x + 1 = 0

B.

6x\(^2\) + x - 1 = 0

C.

3x\(^2\) + x - 1 = 0

D.

6x\(^2\) - x - 1 = 0

Correct answer is D

x = \(\frac{1}{2}\) and x = \(\frac{-1}{3}\) 

(2x - 1) = 0 and (3x + 1) = 0

(2x - 1) (3x + 1) = 0

6x\(^2\) - x - 1 = 0

170.

Make m the subject of the relation k = \(\frac{m - y}{m + 1}\)

A.

m = \(\frac{y + k^2}{k^2 + 1}\)

B.

m = \(\frac{y + k^2}{1 - k^2}\)

C.

m = \(\frac{y - k^2}{k^2 + 1}\)

D.

m = \(\frac{y - k^2}{1 - k^2}\)

Correct answer is B

k = \(\frac{m - y}{m + 1}\)

k\(^2\) = \(\frac{m  - y}{m + 1}\)

k\(^2\)m + k\(^2\) = m - y 

k\(^2\) + y = m - k\(^2\)m

\(\frac{k^2 + y}{1 - k^2}\) = m\(\frac{(1 - k^2)}{1 - k^2}\)

m = \(\frac{y + k^2}{1 - k^2}\)