WAEC Mathematics 2015 Objective — Question 33

Question 33 of 50 from the West African Examinations Council (WAEC) Mathematics 2015 Objective paper, with the correct answer and a full explanation.

In the diagram, line QT and line PR are straight lines, ∠ROS=(3n−20)°, ∠POT=2m°, ∠SOT=n°, ∠POL=m° and ∠QOL is a right angle. Find the value of n°.

• A. 35°Correct
• B. 40°
• C. 55°
• D. 60°

Explanation

Since QT is a straight line, m°+2m°+90°=180°, giving m=30. Since PR is also straight, 2m°+n°+3n°−20°=180°, substituting m=30 gives 60+4n−20=180, so 4n=140, n=35.

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