Supplementary and complementary angles

Chapter 5 Class 7 Lines and Angles
Concept wise

Let’s do this by examples

### Find supplementary angle of 100°

Given angle  = 100°

We know that,

If two angles are supplementary, their sum is 180°

So,

Angle 1 + Angle 2 = 180°

100° + Angle 2 = 180°

Angle 2 = 180° − 100°

Angle 2 = 80°

So, supplementary of 100° is 80°

### Find supplementary angle of 90°

Given angle  = 90°

We know that,

If two angles are supplementary, their sum is 180°

So,

Angle 1 + Angle 2 = 180°

90° + Angle 2 = 180°

Angle 2 = 180° − 90°

Angle 2 = 90°

So, supplementary of 90° is 90°

### Find supplementary angle of 55°

Given angle  = 55°

We know that,

If two angles are supplementary, their sum is 180°

So,

Angle 1 + Angle 2 = 180°

55° + Angle 2 = 180°

Angle 2 = 180° − 55°

Angle 2 = 125°

So, supplementary of 55° is 125°

### Find supplementary angle of 125°

Given angle  = 125°

We know that,

If two angles are supplementary, their sum is 180°

So,

Angle 1 + Angle 2 = 180°

125° + Angle 2 = 180°

Angle 2 = 180° − 125°

Angle 2 = 55°

So, supplementary of 125° is 55°

### Among two supplementary angles, the measure of the larger angle is 44° more than the measure of the smaller. Find their measure .

Let larger angle be ∠1

and smaller angle be ∠2.

Given,

∠1 = ∠2 + 44°

We know that,

If two angles are supplementary, their sum is of 180°

∴∠1 + ∠2 = 180°

(∠2 + 44°) + ∠2 = 180°

∠2 + 44° + ∠2 = 180°

∠2 + ∠2 = 180° − 44°

2 × ∠2 = 136°

∠2 = (136°)/2

∠2 = 68°

Now,

∠1 = ∠2 + 44°

∠1 = 68° + 44°

∠1 = 112°

So, Required angles are of 112° and 68 °

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