Mathematics carries the highest weight in AISSEE — 150 of 300 marks in Class 6 and 200 of 400 marks in Class 9 — and it is also a key section of the RMS CET. Practise these 10 MCQs on Parallel Lines and Triangles, then check your answers and step-by-step solutions in the answer key at the end.
Quick facts: AISSEE 2027 will be held on Sunday, 31 January 2027. There is no negative marking, so attempt every question. Online applications are open until 2 December 2026 on exams.nta.nic.in/sainik-school-society.
Practice Questions
Q1. Two parallel lines are cut by a transversal. If one alternate interior angle is 72°, the other alternate interior angle is ________.
(A) 108°
(B) 144°
(C) 72°
(D) 288°
Q2. Two straight lines intersect. One of the angles formed is 75°. What is the vertically opposite angle?
(A) 105°
(B) 285°
(C) 75°
(D) 165°
Q3. In an isosceles triangle, the angles opposite the equal sides are ________.
(A) supplementary
(B) 90° each
(C) unequal
(D) equal
Q4. In a triangle, the two interior opposite angles of an exterior angle are 40° and 65°. Find the exterior angle.
(A) 75°
(B) 105°
(C) 25°
(D) 255°
Q5. The vertex angle of an isosceles triangle is 100°. What is each base angle?
(A) 100°
(B) 80°
(C) 50°
(D) 40°
Q6. Two parallel lines are cut by a transversal. If one interior angle on the same side is 110°, what is the other?
(A) 110°
(B) 20°
(C) 70°
(D) 250°
Q7. Two straight lines intersect. One of the angles formed is 112°. What is the vertically opposite angle?
(A) 112°
(B) 68°
(C) 248°
(D) 82°
Q8. The exterior angle of a triangle is equal to ________.
(A) the adjacent interior angle
(B) the sum of the two interior opposite angles
(C) 90°
(D) 180°
Q9. The vertex angle of an isosceles triangle is 50°. What is each base angle?
(A) 65°
(B) 50°
(C) 130°
(D) 75°
Q10. Two parallel lines are cut by a transversal. If one corresponding angle is 110°, what is the other corresponding angle?
(A) 110°
(B) 70°
(C) 20°
(D) 250°
Answer Key with Explanations
(C) 72° — Alternate interior angles are equal.
(C) 75° — Vertically opposite angles are always equal.
(D) equal — Base angles of an isosceles triangle are equal.
(B) 105° — Exterior angle = sum of interior opposite angles = 40 + 65 = 105°.
(D) 40° — Base angles = (180 − 100) ÷ 2 = 40°.
(C) 70° — Co-interior angles on the same side add up to 180°.
(A) 112° — Vertically opposite angles are always equal.
(B) the sum of the two interior opposite angles — This is the exterior angle property of a triangle.
(A) 65° — Base angles = (180 − 50) ÷ 2 = 65°.
(A) 110° — Corresponding angles formed by parallel lines are equal.
How did you score?
9–10 correct: excellent — move on to a full-length mock test. 6–8: good — revise the explanations of the questions you missed. Below 6: study this topic again from your NCERT book and retry these questions after two days.
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