Question

Q14. For what value of x the lines AB and CD be parallel?
3x
A
B
90°
С
D​

Answer 1

Step-by-step explanation:

Draw a line parallel to AB and CD and passing through E as shown in the figure which divides x in ∠1 and ∠2

Now AB∣∣EF and ang BE is transversal

∴∠1+120∘=180∘  (Sum of angles made on side side of transversal is supplementary)

⇒∠1=180∘−120∘⇒∠1=60∘

Also DC∣∣EF and DE is transversal

∴∠2+140∘=180∘  (Sum of angles made on side side of transversal is supplementary)

⇒∠2=180∘−140∘⇒∠1=40∘ 

x=∠1+∠2⇒x=60∘+40∘=100∘