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In a 500 m race, the ratio of speeds of two participants, A and B, is 4:5 respectively. If A has a start of 180 m, then the distance by which A wins is

Solution

✅ Correct Option: 1

The total race distance is 500 m. A gets a head start of 180 m, and the speed ratio of A:B is 4:5.


A starts at 180 m and needs to reach 500 m.

Distance A needs to run =500−180=320= 500 - 180 = 320 m

B starts at 0 m and needs to reach 500 m.

Distance B needs to run =500= 500 m


Given speed ratio A:B =4:5= 4:5

Let A's speed =4x= 4x and B's speed =5x= 5x

Time taken by A to finish:

Time=DistanceSpeed\text{Time} = \dfrac{\text{Distance}}{\text{Speed}}

Time for A=3204x\text{Time for A} = \dfrac{320}{4x}

Time for A=80x\text{Time for A} = \dfrac{80}{x}

Time taken by B to finish:

Time for B=5005x\text{Time for B} = \dfrac{500}{5x}

Time for B=100x\text{Time for B} = \dfrac{100}{x}

Since 80x<100x\dfrac{80}{x} < \dfrac{100}{x}, A finishes first.


When A crosses the finish line at time =80x= \dfrac{80}{x}, the distance covered by B is:

Distance=Speed×Time\text{Distance} = \text{Speed} \times \text{Time}

Distance by B=5x×80x\text{Distance by B} = 5x \times \dfrac{80}{x}

Distance by B=400\text{Distance by B} = 400 m


When A finishes at 500 m, B is at 400 m.

Distance by which A wins =500−400=100= 500 - 400 = 100 m

Therefore, A wins by 100 m.

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