Question

5 oranges cost $2. Find the cost of 20 oranges.

Answer 1

$8

Explanation:

if 5 oranges cost $2 then 1 orange costs 2/5 of a dollar, or 40 cents

20 oranges multiplied by 40 cents is $8

or you can set up a proportion:

2/5 = x/20

cross-multiply to get:

5x = 40

x = 8

Answer 2

Answer: $8

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Work Shown:

(5 oranges)/(2 dollars) = (20 oranges)/(x dollars)

5/2 = 20/x

5x = 2*20 .... cross multiply

5x = 40

x = 40/5 .... dividing both sides by 5

x = 8

20 oranges cost $8

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Another way to approach the problem is to note that the jump from "5 oranges" to "20 oranges" is "times 4".

5*4 = 20

So we'll apply the "times 4" operation to the old cost of $2 to get the new cost being 2*4 = 8 dollars