"An airline runs a commuter flight between Portland, Oregon and Seattle, Washington, which are 145 miles apart. If the average speed of the plane could be increased by 40 miles per hour, the travel time would be decreased by 12 minutes. What airspeed is requried to obtain this decrease in travel time? Round your result to one decimal place." The answer the book gives is 191.5. I get stuck pretty much at the beginning. I get the following: d r t ---------------- 145 | r | t 145 | r - 40 | t - 12 and then have a brain fart. How would you go about solving a problem like this?
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It would seem that there isn't enough info to answer or calculate the airspeed. This is why. in order to solve this problem, you need to know three things: the Distance=d, the rate=r, and the time it takes for the trip=t. the problem if worked in a couple of different ways would have two variables, as you indicated. The distance is 145 miles, the rate is r+40 not minus, and the time is t-12. when you put the two variables in the problem it takes you on a trip alright... the formula is d=rt. You cant take and plug in all the information given at one time. You have to solve for the variable of "What airspeed is requried to obtain this decrease in travel time?" airspeed is RATE. First you have to figure out what the original rate of speed was. Ok, you say that the original rate is r+40. ok, then plug in what you have... d= r x t 145 = (r +40)(t) or if you want to get complicated 145 = (r +40)(t-12) you just need more information... Let me know if you get this one...I would be interested to know how you guys get it... a1
