A car traveling at a certain constant speed takes 5 seconds longer to travel 1 km than it would take to travel 1 km at 90 km/hour. At what speed, in km/hr, is the car traveling?	Choices.
A) 70 B) 80 C) 74 D) 75 E) 78
Time to cover 1 kilometer at 80 kilometers per hour is 1/90 hours = 3,600/90 seconds = 40 seconds;   Time to cover 1 kilometer at regular speed is  40 + 5= 
<gadget id="calculator"> 40 + 5</gadget>
<output>45</output>
45 seconds= 45/3,600 hours = 1/80 hours;   So, we get that to cover 1 kilometer 1/80 hours is needed --&gt; regular speed 80 kilometers per hour (rate is a reciprocal of time or rate=distance/time).   Answer: 80.
<result>B</result>
A car traveling at a certain constant speed takes 5 seconds longer to travel 1 km than it would take to travel 1 km at 90 km/hour. At what speed, in km/hr, is the car traveling?