Kinematic Concepts - Mission KC7 Detailed Help

A rightward-moving car accelerates from 55 mi/hr to 25 mi/hr in 4.2 seconds. Determine the average acceleration of the car in mi/hr/s.
(Note: Numbers are randomly generated and may differ from those shown here.)

Acceleration (a) is the rate of change in an object's velocity. It is determined from knowledge of a velocity change (Δv) and the change in time (Δt) over which the velocity changes.
a = Δvelocity / Δtime = Δv / Δt

The numerator in the acceleration equation (see Formula Fix section) is the change in velocity. A changein any value is found by subtracting the initial value from the final value. In this question, such a change will be negative. But don't be fooled! The question asks you to enter the magnitude of the acceleration; ignore + and - signs which are indicators of a direction.

The Minds On Physics program calculates answers accurate to several decimal places. Your answer does not need to be that precise. The program will allow you to have a 1% deviation from the right answer without being wrong. This means you should enter your answer to at least the second decimal place.