SAT Math: Interpreting the y-intercept in Context
35+ practice questions in Praczo
The concept, explained
- 1
The y-intercept (b in y = mx + b) is the value of y when x = 0.
- 2
In a real-world scenario, the y-intercept represents the starting point, initial value, base fee, or flat rate.
- 3
Look for phrases like "initial amount," "upfront cost," "starting population," or "value at year 0."
- 4
Make sure x = 0 makes sense in the context of the problem; if x represents years since 2010, the y-intercept is the value in 2010.
- 5
The x-intercept, by contrast, represents when the output reaches zero (e.g., when a tank is fully emptied).
- ✗ Confusing the y-intercept (initial amount) with the slope (rate of change).
- ✗ Assuming the y-intercept represents the final amount or the total capacity rather than the starting condition.
SAT-style practice
The total cost C, in dollars, to rent a truck for d days is given by C = 45d + 60. What does the 60 represent?
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