MathRevolution wrote:

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Math Revolution GMAT math practice question]

After \(t\) seconds, the height of a ball from the ground is given by the equation \(h =-9.8t^2+ft+g\) (\(f\) and \(g\) are constants). If the ball is at its maximum height, then \(t=?\)

1) \(f = 10\)

2) \(g = 10\)

\(f(x) = ax^2 + bx + c\) is the equation of a parabola.

If a<0, then the parabola opens DOWNWARD, with a maximum value when:

\(x = \frac{-b}{2a}\)

Given quadratic:

\(h = -9.8t^2 + ft + g\)

Here, the maximum height will be yielded when:

\(t = \frac{-f}{(2 * -9.8)}\)

Thus, to determine what value of t will yield the maximum height, we need to know the value of f.

Statement 1: f=10

SUFFICIENT.

Statement 2: g=10

No information about f.

INSUFFICIENT.

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