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SSC GD 2023 PYQ — Question 53

SSC GD Constable (English) - 6 Feb 2023 - Shift 4 • Quantitative Aptitude • Q53

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The Rajdhani train travels in a straight line at a constant speed of 75 km/h for a particular distance 'd' and then travels another distance equal to '2d' at a constant speed of 100 km/h in the same direction as earlier. Find the average speed of the train during the whole journey ?

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Correct answer: B

Explanation

The correct answer is Option 2 i.e. 90 km/h.

Given:

Speed of train for d km = 75 km/h

Speed of train for 2d km = 100 km/h

Formula Used:

Time=DistanceSpeedTime = {Distance\over Speed}

Average speed=Total DistanceTotal TimeAverage\ speed = {Total\ Distance\over Total\ Time}

Explanation:

Let the value of d be 150 km.

We know that,

Time taken in first travel = d75d \over 75

⇒ 15075150 \over 75 = 2 hr

Time taken in second travel = ​​2d100​​2d \over 100

⇒ ​​2×150100​​2\times 150 \over 100 = 3 hr

Now, Average speed = (150 + 300)/(3 + 2)

⇒ 450/5 = 90 km/hr