WAEC Mathematics Past Questions & Answers - Page 176

876.

Simplify: \(\frac{2}{3xy} - \frac{3}{4yz}\)

A.

\(\frac{2-x}{12xyz}\)

B.

\(\frac{2z-3x}{12xyz}\)

C.

\(\frac{4z-3x}{12xyz}\)

D.

\(\frac{8z-9x}{12xyz}\)

Correct answer is D

\(\frac{2}{3xy} - \frac{3}{4yz} = \frac{2(4)-3(3x)}{12xyz} = \frac{8z-9x}{12xyz}\)

877.

A regular polygon has 9 sides. What is the size of one of its exterior angles?

A.

20o

B.

40o

C.

90o

D.

140o

Correct answer is B

Exterior angle \(=\frac{360}{n}\) where n = no of sides
\(=\frac{360}{9}=40^{\circ}\)

878.

The salary of a man was increased in the ratio 40:47. calculate the percentage increase in the salary

A.

85.1%

B.

58.5%

C.

17.5%

D.

14.9%

Correct answer is C

\(\%Increase = \frac{Actual \hspace{1mm}increase}{initial \hspace{1mm}ratio}\times 100\%\)
Actual increase = 7; Initial ratio = 40
\(=\left(\frac{7}{40} \times 100\%\right)=\frac{35}{2}=17.5\%\)

879.

A train moving at a uniform speed covers 36km in 21 minutes. How long does it take to cover 60km?

A.

35 mins

B.

40 mins

C.

45 mins

D.

90 mins

Correct answer is A

Since 36km in 21 minutes
1km in \(\frac{21}{36}\)minutes
60km in \(\left(\frac{21}{36}\times 60\right)\)minutes = \(\frac{70}{2}\)min
= 35 mins

880.

P = {3, 9, 11, 13} and Q = {3, 7, 9, 15} are subset of the universal set ξ = {1, 3, 7, 9, 11, 13, 15} find PI ∩ QI

A.

{3, 9}

B.

{5, 7, 9}

C.

{1}

D.

{1, 11}

Correct answer is C

PI = {1, 7, 15} ; QI = {1, 13, 11}
PI ∩ QI = {1}