Question

In the given figure, find out which pair of lines are parallel:

Answer 1

From the given figure,

∠1 = 180° – 123°  ......[Linear pair]

⇒ ∠1 = 57°

Also, ∠2 = 180° – 57°   ......[Linear pair]

⇒ ∠2 = 123°

Now, ∠1 + ∠2 = 57° + 123° = 180°, then the lines are parallel

It sum of the consecutive angles are 180°, then the lines are parallel.

∴ EF || GH

Now, ∠3 = 180° – ∠2  ......[Linear pair]

⇒ ∠3 = 180° – 123° = 57°

Also, ∠4 = 180° – 55° = 125°  ......[Linear pair]

∴ ∠3 + ∠4 = 57° + 125° = 182° ≠ 180°

So, GH and KP are not parallel.

Also, ∠3 + 122° = 57° + 122° = 179° ≠ 180° 

Hence, AB and CD are not parallel.