## Lines and Angles

In the figure shown above, four line segments join at a single point to form four angles. What is the value of a?

A. 10

B. 18

C. 20

D. 35

E. 40

## Knowsys Method

**Read the question carefully.** Make note that the figure is not drawn to scale, so the sizes of the angles in the picture do not reflect their true measurements.

**Identify the bottom line.** a = ?

**Assess your options**. Visualize the point in the center as the center of a circle. The number of degrees around the center point is 360, just like the number of degrees around the center of a circle. That means that all of these angle measurements should add together to equal 360 degrees. If you set that up as an equation, then you can solve for a.

**Attack the problem. ** Set up your equation and find the value of a.

2a + 4a + 5a + 7a = 360

18a = 360

÷18 ÷18

a = 20

**Loop back.** Did you find the value of a? Yes. All that is left is to select the letter of the correct answer.

The correct answer is (C).

This is a medium level question.