Question

Points D, B, and E are collinear. Find the value of a so that points A, B, and C

are collinear.

Answer 1

Since A, O and B are collinear,

i.e.,

∠

A

O

B

=

180

∘

or,

∠

A

O

D

+

∠

D

O

C

+

∠

B

O

C

=

180

∘

(

x

−

10

)

∘

+

(

4

x

−

25

)

∘

+

(

x

+

5

)

∘

=

180

∘

Or,

x

+

4

x

+

x

−

10

∘

−

25

∘

+

5

∘

=

180

∘

Or,

6

x

−

30

∘

=

180

∘

Or,

6

x

=

180

∘

+

30

∘

=

210

∘

Or,

x

=

210

∘

6

=

35

∘

∠

B

O

C

=

x

+

5

∘

=

35

∘

+

5

∘

=

40

∘