Quick questions on Straight-line depreciation for HSC Maths Standard 2

Because the same $5500 comes off every year, the value of the ute drops in equal steps, the signature of a straight line. Building the table from $S = 48\,000 - 5500n$ gives

Sometimes the depreciation is quoted not as a dollar amount but as a percentage of the original cost each year. This is still straight-line depreciation, because the percentage is always taken from the same purchase price, so the dollar amount removed each year is constant. Convert the rate to a dollar amount once with $D = \text{rate} \times V_0$, then use $S = V_0 - Dn$ as normal. For office equipment bought at $15\,000 depreciating at $20\%$ of the original cost a year, the annual amount is $D = 0.20 \times 15\,000 = 3000$, so the equipment loses the same $3000 every year and the value falls in a straight line.