We can find a ratio between the rates of increase and decrease for the corn and wheat:
To get rid of the radical sign in the denominator, we can multiply top and bottom by
This ratio indicates that for every cent that the price of wheat decreases, the price of corn increases by
cents. So if the price of wheat decreases by x cents, the price of corn will increase by
Since the difference in price between a peck of wheat and a bushel of corn is current ly $2.60 or 260 cents, the amount by which the price of corn increases plus the amount by which the price of wheat decreases must equal 260 cents. We can express this as an equation:
Amount Corn Increases + Amount Wheat Decreases = 260 We can then rewrite this word equation using variables. Let c be the decrease in the price of wheat in cents:
Notice that the radical 2 was replaced with its approximate numerical value of 1.4 because the quest ion asks for the approximate price. We need not be exact in this particular instance.
If c = 20, we know that the price of a peck of wheat had decreased by 20 cents when it reached the same level as the increased price of a bushel o f corn. Since the original price of a peck of wheat was $5.80, its decreased price is $5.80 - $0.20 = $5.60. (By the same token, since c = 20, the price of a bushel of corn had increased by
cents when it reached the same level as the decreased price of a peck of wheat. This is equivalent to an increase of approximately 240 cents. Thus the increased price of a bushel of corn = $3.20 + $2.40 = $5.60.)