Question

47. The following quadratic formula can be used to approximate the distance in feet, that it takes to stop after the brakes are applied for a car traveling on a dry road at the rate of thousands per hour: d=0.045r^2+1.1r. To the nearest foot, how far will a car travel once the brakes are applied at (a) 40 mph, (b) 55 mph, and (c) 65 mph?

Answer 1

Thousands?

$d(r) = 0.045r^2 + 1.1 r$

$d(40) = 0.045(40^2) + 1.1(40) = 116 \textrm{ feet}$

$d(55) = 0.045(55^2) + 1.1(55) = 196.625 \textrm{ feet}$

$d(55) = 0.045(65^2) + 1.1(65) = 261.625 \textrm{ feet}$

Answer: a) 116 b) 197 c) 262