A car traveling at a certain constant speed takes 2 seconds longer to travel 1 kilometer than it would take to travel 1 kilometer at 80 kilometers per hour. At what speed, in kilometers per hour, is the car traveling? Pick:	A) 71.5	B) 72	C) 72.5	D) 73	E) 76.6
Many approaches are possible, one of them:   Let the distance be 1 kilometer.   Time to cover this distance at 80 kilometers per hour is 1/80 hours = 3,600/80 seconds = 45 seconds;   Time to cover this distance at regular speed is 45+2= 
<gadget id="calculator">45+2</gadget>
<output>47</output>
47 seconds= 47/3,600 hours = 5/383 hours;   So, we get that to cover 1 kilometer 1/(5/383) hours is needed --&gt; regular speed 76.6 kilometers per hour (rate is a reciprocal of time or rate=distance/time).   Answer: 76.6
<result>E</result>
A car traveling at a certain constant speed takes 2 seconds longer to travel 1 kilometer than it would take to travel 1 kilometer at 80 kilometers per hour. At what speed, in kilometers per hour, is the car traveling?