Final answer:
To find the value of f(x) when x=8 for a function that varies directly with x, first calculate the constant of proportionality with the given values, then use that constant to find the new value of f(x), and round to the nearest whole number.
Step-by-step explanation:
If f(x) varies directly with x, it means that f(x) = k * x, where k is the constant of proportionality. Given that f(x) = 120 when x = 45, we can find k by rearranging the formula: k = f(x) / x which gives us k = 120 / 45. After finding k, you can use it to find the value of f(x) when x = 8 by plugging it back into the formula f(x) = k * x. The calculation will go as follows:
- Find the constant k: k = 120 / 45 = 2.67
- Use k to find f(x) when x = 8: f(x) = 2.67 * 8 = 21.36
- Round off to the nearest whole number: f(x) ≈ 21
Therefore, the value of f(x) when x = 8 is approximately 21.