The graph shows the relationship between the total cost and the number of gift cards that raj bought for raffle prizes.

The problem is as following:

The 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 Or $110

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Solution:

The points of the figure represents a straight line

The general form of the straight line is  ⇒ y = mx + c

where m is the slope and c is constant

let x ⇒ The number of gifts cards , y ⇒ Total cost (in $)

we will find m and c using the points (1,20) , (2,40)

The slope = m =

∴ y = 20x + c

Substitute with the point (1,20) ⇒ y = 20 at x = 1

∴ 20 = 20 * 1 + c

∴ 20 = 20 + c

∴ c = 0

∴ The equation of the line ⇒⇒⇒ y = 20x

To find the cost for 5 of the gift cards substitute with x = 5

∴ y = 20 * 5 = 100

So, the cost for 5 of the gift cards = $100

The correct answer is option 3 ⇒⇒⇒ $100

i leave the calculator work to you.

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