Question

he graph shows the relationship between the total cost and the number of gift cards that Raj bought for raffle prizes. What would be the cost for 5 of the gift cards? $80 $90 $100 $110

Answer 1

Answer: C. $100.

Solution:

Concept: “The relationship of the given curve should be established”

Given Diagram shows that the relationship between both the axes are linear, which means a straight line.

The straight line equation is governing by,

               y = mx +c

where, m - slope

c – constant.

Consider two points (1, 20) and (2, 40)

Slope,

             $m=\frac { ({ y }_{ 2 }-{ y }_{ 1 }) }{ ({ x }_{ 2 }-{ x }_{ 1 }) } =20$

Governing equation becomes,

y = 20x + c;

Constant, using point (1,20)

y = 20

∴ c = 0

Hence, the equation of given chart is

               y = 20x;

To find cost of 5 gifts,

On substituting x = 5,

               y = $20 \times 5$ = 100

Thus, the cost = $100