SAT Mathematics Practice Test 7

The value of the camera equipment depreciates from its original purchase value at a constant rate for 12 years. So if x is the amount, in dollars, by which the value of the equipment depreciates each year, the value of the camera equipment, in dollars, t years after it is purchased would be 32,400 – xt. Since the value of the camera equipment after 12 years is $\mathrm{\$}0$, it follows that 32,400 – 12x = 0. To solve for x, rewrite the equation as 32,400 = 12x. Dividing both sides of the equation by 12 gives x = 2,700. It follows that the value of the camera equipment depreciates by $\mathrm{\$}2,700$ each year. Therefore, the value of the equipment after 4 years, represented by the expression 32,400 – 2,700(4), is $\mathrm{\$}21,600$.