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प्रश्न
In the given diagram (not drawn to scale), railway stations A, B, C, P and Q are connected by straight tracks. Track PQ is parallel to BC. The time taken by a train travelling at 90km/hr to reach B from A by the shortest route is:
पर्याय
8 minutes
12 minutes
16.8 minutes
20 minutes
MCQ
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उत्तर
20 minutes
Explanation:
PQ || BC
So, ΔAPQ ∼ ΔABC and `(PQ)/(BC) = 20/50 = 2/5`.
Hence, `(AP)/(AB) = 2/5`.
Let AP = x and PB = 18.
So, AB = x + 18 and `x/(x + 18) = 2/5`
⇒ 5x = 2x + 36
⇒ x = 12 km
So, AB = 30 km.
Time = `"Distance"/"Speed"`
= `(30 km)/(90 km) xx hr^-1`
= `1/3 hr`
= 20 minutes
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