- AObtuse
- BAcute
- CRight
- DReflex
Step-by-Step Solution
A linear pair sums to 180°. If one is acute (< 90°), the other must be more than 90° (obtuse) to make the total 180°.
Answer: A) Obtuse
Two angles are said to be a linear pair. If one angle is acute, what must the other angle be?
Class 7Lines and AnglesLines and Angles
Key idea: Vertically opposite angles
When two straight lines cross, four angles form at the intersection. The two angles directly **across** the vertex (sharing only the vertex, not a side) are called **vertically opposite** — and they are always equal.
If one angle is 70°, then:
- Its vertical opposite is also 70°.
- The other two angles are each 110° (linear pair with 70°).
Why? Each pair forms a linear pair with a common neighbour, both summing to 180° — so the opposites end up equal.
If one angle is 70°, then:
- Its vertical opposite is also 70°.
- The other two angles are each 110° (linear pair with 70°).
Why? Each pair forms a linear pair with a common neighbour, both summing to 180° — so the opposites end up equal.
Master this chapter in 30 minutes a day.
Don't just memorise the answer — build a daily practice habit.
Practice 5 Similar Questions Free →All Lines and Angles practice questions
More Class 7 Lines and Angles practice
Two parallel lines are cut by a transversal. One angle is 64°. What is the measure of…Which of these is the correct statement?Two parallel lines are cut by a transversal so that the two interior angles on the same…A transversal cuts two lines l and m. The two interior angles on the same side of the…A transversal cuts lines a and b. A pair of alternate interior angles both measure 58°.…