# NCERT Class 7 Mathematics Solutions: Chapter 5 –Linear and Angles Exercise 5.1 Part 3

Get unlimited access to the best preparation resource for IMO-Level-2 : Get full length tests using official NTA interface: all topics with exact weightage, real exam experience, detailed analytics, comparison and rankings, & questions with full solutions.

1. Find the angle which is equal to its supplement.

Consider the angle be .

Supplement of this angle is also .

The sum of the measures of a supplementary angle pair is .

So, is equal to its supplement.

2. In the given figure, are supplementary angles. If is decreased, what changes should take place in so that both the angles still remain supplementary.

are supplementary angles.

If is reduced, then should be increased by the same measure so that this angle pair remains supplementary.

3. Can two angles be supplementary if both of them are:

(i) Acute?

(ii) Obtuse?

(iii) Right?

(i) No. Acute angle is always lesser than .

It can be observed that two angles, even of , cannot add up to .

So, two acute angles cannot be in a supplementary angle pair.

(ii) No. Obtuse angle is always greater than .

It can be observed that two angles, even of , will always add up to more than .

So, two obtuse angles cannot be in a supplementary angle pair.

(iii) Yes. Right angles are of and

So, two right angles form a supplementary angle pair together.