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In a car race, car AA beats car BB by 45 km45 \mathrm{~km}, car BB beats car CC by 5050km, and car AA beats CC by 90 km90 \mathrm{~km}. the distance (in km) over which the race has been conducted is

Solution

✅ Correct Option: 4

We need to set up relationships between the cars' performances and use the concept of relative speeds.

Let us define the race distance as x km.


When the race ends (i.e., when car A finishes):

Car A travels = x km (full race distance)

Car B travels = (x - 45) km (since A beats B by 45 km)

Car C travels = (x - 90) km (since A beats C by 90 km)


This means when car B completes the full race distance of x km, car C has only covered (x - 50) km.

Here's the key insight: The speed ratio between any two cars remains constant throughout the race.


From the first condition, the speed ratio of B to C is:

Distance covered by BDistance covered by C=x−45x−90\dfrac{\text{Distance covered by B}}{\text{Distance covered by C}} = \dfrac{x - 45}{x - 90}

From the second condition, when B covers the full race distance x, C covers (x - 50):

Distance covered by BDistance covered by C=xx−50\dfrac{\text{Distance covered by B}}{\text{Distance covered by C}} = \dfrac{x}{x - 50}

Since the speed ratio is constant:

x−45x−90=xx−50\dfrac{x - 45}{x - 90} = \dfrac{x}{x - 50}


(x−45)(x−50)=x(x−90)(x - 45)(x - 50) = x(x - 90)

x2−50x−45x+2250=x2−90xx^2 - 50x - 45x + 2250 = x^2 - 90x

x2−95x+2250=x2−90xx^2 - 95x + 2250 = x^2 - 90x

−95x+2250=−90x-95x + 2250 = -90x

2250=5x2250 = 5x

Therefore: x = 450 km


Answer: The race distance is 450 km.

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