### Home > PC3 > Chapter 7 > Lesson 7.2.2 > Problem7-86

7-86.

The same car from problem 7-80 travels $d(t)=10t^2$ feet in the first $t$ seconds after it starts. Calculate the average velocity on each of the intervals as they approach $t=4$ seconds.

1. $4\le t\le5$

$\frac{\Delta d}{\Delta t} = \frac{10(5)^2 - 10(4)^2}{5 - 4}$

1. $4\le t\le4.1$

$\frac{\Delta d}{\Delta t} = \frac{10(4.1)^2 - 10(4)^2}{4.1 - 4}$

1. $4\le t\le4.01$

1. $3.99\le t\le4$

1. $3.999\le t\le4$