Question

Which of the following line represents a proportional relationship between time and amount of money you spent?

• A. Line 1
• B. Line 3
• C. Line 4
• D. Line 2

Answer 1

The correct option is B Line 3

x and y said are to be in a proportional relationship, if

i) The ratio between y and x is constant.
ii) The graph of the function passes through the origin (0,0).

Let us consider Line 1:


Slope is constant, as it is a straight line.
It does not pass through the origin (0,0).

Therefore, it does not represent a proportional relationship.

Let us consider Line 2:


Slope is constant, as it is a straight line.
Thus it does not pass through the origin (0,0).

Therefore, it does not represent a proportional relationship.

Let us consider Line 3:


Slope is constant, as it is a straight line.
It passes through the origin (0,0).

Therefore, it represents a proportional relationship.

Let us consider Line 4:


Slope is not constant as it is a straight line but at (1,20) slope becomes 0.

It also passes through the origin (0,0).

Therefore, it is not representing a proportional relationship.

So, only Line 3 represents a proportional relationship.