# In the given figure AOB is a simple line and OC is indicated on this :

In the given figure AOB is a simple line and OC is indicated on this. If a: b = 2: 1, then the value of a is

(a) 80^{o}

(b) 100^{o}

(c) 120^{o}

(d) 140^{o}

**Answer: (c) (c) 120 ^{o}.**

**Solution:-**

a: b = 2: 1 (Given)

a/b = 2/1

a = 2b ……………………. (1)

As, we know that the sum of all angles to make on a straight is 180^{o}.

Then, a + b = 180

From equation (1),

2b + b = 180

3b = 180

b = 180/3

b = 60^{o}

Then, a = 2b => 2 x 60

= 120^{o}

So, the value of a will be 120^{o}.

Hence, the correct answer is option (c) 120^{o}.

120°

a:b=2:1

total=2+1=3parts

3parts=180° then 1part=180°/3=60°

required a=2parts=>2*60=120°