An unknown starting split and different changes for two sites call for percent-change multipliers. Treat the first year's total as , then use the known combined change to find each site's starting share with a Desmos regression. Keep the sites separate through both years: applying either site's second-year rate to the combined total gives the wrong result.
Hints
- Hint 1
A starting share is one site's portion of the 2023 total. Call Site A's share , so Site B's is . What multiplier takes each site from 2023 to 2024?
- Hint 2
The combined increase means the 2024 total is times the 2023 total. Add the sites' 2024 amounts, each measured against the 2023 total, and set their sum equal to .
- Hint 3
A successive percent change acts on the amount from the year before. Site A keeps of its 2024 boxes, while Site B has of its 2024 boxes. Multiply each site by both yearly factors before adding.
Step-by-step
Track each site's share
Step 1Write the 2024 total in terms of the 2023 shares
Treat the 2023 combined total as . Let be Site A's share, or portion, of that total; Site B's share is . An increase multiplies A by , and a decrease multiplies B by . The combined increase makes the 2024 total , so add the two site amounts:
- Step 2
Find the starting split
Type in Desmos, using for . The tells Desmos to fit the unknown value; under PARAMETERS it shows . So Site A had of the 2023 total, and Site B had the remaining .
- Step 3
Carry each site through 2025
A factor is the number that multiplies an amount after a percent change. A's decrease gives of its 2024 amount; B's increase gives of its 2024 amount. Type the two lines below, naming their 2025 amounts and . Desmos shows and , each measured against the 2023 total.
- Step 4
Add the 2025 site amounts
Type . Desmos prints , the overall factor comparing the 2025 combined total with the 2023 combined total. Don't apply one site's 2025 factor to the 2024 combined total: the sites changed at different rates.
- Step 5
Convert the factor to a percent increase
The original total is , so subtract to get only the increase. Then multiply by to express it as a percent. Type ; Desmos prints . The combined number of boxes increased by from 2023 to 2025. Grid in 0.384.