CPM Homework Help : CALC Problem 7-64

The velocity of a plane flying from San Francisco is:

$v(t) = 270\sqrt { t }$

where $t$ is measured in hours and $v(t)$ in miles per hour. Find the average velocity of the plane between the 1st and 4th hours.

Hint:

You are given a velocity function and you want to find average velocity.
Should you use 'average area under the curve' or 'slope of the secant'?