Test Index

WAEC Mathematics 2015 Paper

© africaexams.com

Question : 30

Total: 45

In the given diagram,

\overline{QT}

\overline{PR}

are straight lines, < ROS = (3n - 20), < SOT = n, < POL = m and < QOL is a right angle. Find the value of n.

35^o
40^o
55^o
60^o

Solution:

Concept:

Angles on a straight line add up to

180^\circ

.

Explanation:

From the diagram, the angles along straight line

POR

are

m

,

90^\circ

and

2m

.

So,

m + 90^\circ + 2m = 180^\circ

3m = 90^\circ

m = 30^\circ

.

Using straight line

QT

:

\angle QOR + \angle ROS + \angle SOT = 180^\circ

2m + (3n - 20^\circ) + n = 180^\circ

Substitute

m = 30^\circ

:

60^\circ + 3n - 20^\circ + n = 180^\circ

4n + 40^\circ = 180^\circ

4n = 140^\circ

n = 35^\circ

.

Answer:

n = 35^\circ

, which is option A.

© africaexams.com

Go to Question:

Prev Question

Next Question