When a truck travels at 60 miles per hour, it uses 30 percent more gas

I think the gas information is a lot of extra . . . All you need is to see that he is not going to cover 160 miles with 10 gallons of gas driving at 60 mph. I'm wondering if I have my units confused.

At 50mph, he would be able to go 20 miles/gal * 10 gallons = 200 miles

30 percent fewer miles than that, x = miles he can cover?
\(200 = 1.3x\)
\(x =\frac{200}{1.3}=\) approx 154 mi

Conclusion: he has to stop for gas.

TIME to travel?

He is 160 miles from his destination. D/r= time

Time to travel, w/o gas stop:
\(\frac{160}{60}=\frac{8}{3} hrs\) without the gas stop

Time for Gas stop = 20 minutes = 1/3 hr

Time total:\(\frac{8}{3} + \frac{1}{3}=\frac{9}{3}= 3 hrs\)

= 180 minutes

Answer B

Hi Alexey,

You have done a calculation mistake in the portion marked with RED color in your response.

140+ 20=160 not 180

We are given that when a truck travels at 60 miles per hour, it uses 30 percent more gasoline to travel any distance than it does when it travels at 50 miles per hour, and that the truck can travel 20 miles on a gallon of gas if it is traveling at 50 miles per hour. So, when traveling at 60 mph, the truck travels 20/1.3 = 200/13 miles per gallon of gas.

Thus, the number of gallons of gas used in a 160-mile trip is 160/(200/13) = 160 x 13/200 = 10.4, which is more than the 10 gallons of gas the truck has.

The time to drive 160 miles at 60 mph is 160/60 = 16/6 hours = 8/3 hours x 60 = 160 minutes. However, since we have to stop for 20 minutes to fill the truck with gas (recall that we don’t have a sufficient amount of gas for the trip), the total time for the 160-mile trip is 160 + 20 = 180 minutes.

Answer: B

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