At 4:00 PM $29 \mathrm { mi } ^ { 2 }$

Short Answer

At 4:00 P.M. a car's speedometer reads $29 \mathrm { mi } ^ { 2 }$ . At 4:15 it reads $72 \mathrm { mi } / \mathrm { h } ^ { 2 }$ . At some time between $4 : 00$ and $4 : 15$ the acceleration is exactly $x \mathrm { mi } ^ { 2 } \mathrm {~h} ^ { 2 }$ . Find $x$ .