Increasing and decreasing by a given percentage

Task goals

• Increase or decrease a quantity by a given percentage using the decimal-multiplier method (multiply by 1 plus or minus the rate as a decimal).
• Read a percentage-change bar (100% baseline plus a hatched increase or decrease segment) to find the new amount.
• Apply the method to money and real-world contexts (discounts, markups, GST, population growth, single-period depreciation).
• Apply the method with decimal percentage rates and round money answers to the nearest cent.
• Apply two successive percentage changes (same or different rates, increase then decrease or vice versa) and explain why the result is not generally the same as the starting amount.
• Work backwards from an original and a new amount to find the percentage rate of change.