Summary
Highlights
The APES exam includes 6-9% math-based multiple-choice questions and 20% math-based FRQ questions, contributing 12-13% to the final score. FRQ math questions appear on the third FRQ, consisting of three two-point questions. Each point is awarded for correct setup with units and correct answer with units. It is crucial to always include units in both setup and answer.
Memorize the percent change formula: (New - Old) / Old * 100. This formula is frequently tested on both FRQ and multiple-choice sections. An example of calculating percent change in renewable energy investment is provided, illustrating how to identify new and old values and apply the formula. Rounding to the nearest tenth or whole percent is generally acceptable for FRQ answers.
Understand that 'percent' means 'per 100.' To convert a percentage to a decimal for calculations, divide by 100 or move the decimal two places to the left. The video demonstrates how to calculate a percentage of a percentage, using an example of greenhouse gas emissions from agriculture, and emphasizes the importance of showing all steps and including units.
Unit conversion is a key skill. Dimensional analysis is presented as a safe and systematic method. The core rule is to place units on opposite sides of the division line to cancel them out. A simple example of converting meters to kilometers is shown, followed by a more complex multi-step problem involving calculating revenue from water bottle sales, converting liters per day to dollars per week.
Additional calculations that might appear on the exam include Net Primary Productivity (NPP) which is Gross Primary Productivity (GPP) minus respiration. Another common calculation is energy or biomass transfer between trophic levels, using the 'Rule of 10' where only 10% of energy moves to the next level.
To calculate the percent growth rate of a country, subtract the Crude Death Rate (CDR) from the Crude Birth Rate (CBR) and divide by 10. The 'Rule of 70' is taught for calculating population doubling time: divide 70 by the population growth rate as a percent.
Kilowatt-hours (kWh) measure electricity consumption (power over time). Examples include calculating cost savings from energy efficiency and energy usage of a device. The video also covers calculating the half-life of radioactive elements, demonstrating how to determine the remaining mass after a certain number of half-lives or infer the half-life from mass decay over time.