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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

A starts the race 180 m ahead of the starting line, so A only needs to run 320 m while B runs the full 500 m.

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

A starts at 180 m and needs to cover 500180=320500 - 180 = 320 m.


The ratio of speeds is A : B = 4 : 5.

Let A's speed = 4x4x and B's speed = 5x5x.


Time = Distance ÷ Speed

Time taken by A to finish:

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

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


When A finishes at time 80x\dfrac{80}{x}, the distance covered by B is:

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

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

Distance=400\text{Distance} = 400 m


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

Distance by which A wins:

Distance=500400\text{Distance} = 500 - 400

Distance=100\text{Distance} = 100 m

Therefore, A wins by 100 m.

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