While driving at a speed of \(30\) kmph (with available friction \(0.4\)) down the grade, the driver requires a braking distance twice that required for stopping the vehicle when he travels up the same grade. The grade is
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Braking distance on grades:
\[
\boxed{
BD=\frac{V^2}{254(f-G)}
}
\]
for downgrades, and
\[
\boxed{
BD=\frac{V^2}{254(f+G)}
}
\]
for upgrades.