Train X traveled 250miles from the city A to the city B. At

Question

Train X traveled 250miles from the city A to the city B. At the same time, on the straight and parallel line, train Y traveled the same route from the city B to the city A. If two trains, X and Y went toward each other and met in 2hours, which one of them was closer to the arrival city? (1)when train X met train Y, the average speed of train X was 70miles per hour. (2)the average speed of train Y over the whole distance was 55 miles per hour. My answer is A, because (2)does not show the speed per hour during for the first two hours, but someone said the answer is D Could you teach me which one is right?

thanks

whynot · Answer

I'm going with B, Statement II is sufficient by itself.

If we know train Y was traveling at a uniform speed of 55mph, that means it traveled 55mph*2hrs = 110miles when it met train X. Which means train X traveled 250-110= 140miles in two hrs. Train X is closer to the arrival city.

Statement I says train X was traveling 70mph when it met train Y but not that it was traveling 70mph for the entire distance.

briks123 · Answer

I say A.

(1) is sufficient because it is saying that X's average speed for the first two hours had been 70mph. From that, we can calculate the train's distance.

(2) isn't sufficient. It doesn't say that the train was traveling at a uniform speed. It could have easily been going 70mph for the first half of the trip.

I agree with you here. What is the OA?

lanter1 · Answer

Statement 1 is correct...if x avg 70mph for 2 hours then it travels 140 miles in that stretch and y travels tavels 110 and therefore x is closer.

Statement 2 should not be correct...saying that the avg was 55 mph for the whole trip says nothing about the first 2 hours. If the question said they move at a constant rate then this would be enough. For all we know, y averages 70 mph for 2 hours and then much less for the next 110 miles.

zakk · Answer

D is the answer.

They left at the same time. working it out, train x would cover 140 miles in two hours, so Y would be at 110 miles. SUFF

In the other, is says train Y averages 55 mph, so in two hours it would be at 110 miles, where it would meet train X, meaning that train X would cover 140. SUFF

It took me a second, but the info they give would makes both statements sufficient.

*EDIT* reading the explanations the others gave, we DON'T know if Train Y took off like a rocket then stopped for lunch, or if they cruised at 55 all the way. 

I'm wrong with D, I think.

lanter1 · Answer

Allows look for whether the question says constant speed or just average. If they give average look for a specific amount of time.

whynot · Answer

Maybe I'm reading too much into this but all statement I says is that train X was traveling at 70mph when it met train Y. But why does that mean it was traveling 70mph for the entire 2hrs?

leokkim · Answer

They helped me a lot. I think I will go for the answer A.

Train X traveled 250miles from the city A to the city B. At

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