An express train covers a fixed distance in 40 minutes at an average speed of 200 km/h. Due to construction work, it needs to be diverted, increasing the distance by 25%. If the train needs to arrive at its destination on time (in 40 minutes), what should its new average speed be in km/h?

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1. Time = 40 min = $	frac{2}{3}$ h. Original distance = $200	imes	frac{2}{3}=	frac{400}{3}$ km.
2. New distance = $	frac{400}{3}	imes1.25=	frac{500}{3}$ km (25% more).
3. Required speed = $\dfrac{500/3}{2/3}=\dfrac{500}{2}=250$ km/h.
4. So the train must run at 250 km/h to arrive on time.

FINAL_ANSWER: a

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