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Anil, Sunil, and Ravi run along a circular path of length 3 km3 \mathrm{~km}, starting from the same point at the same time, and going in the clockwise direction. If they run at speeds of 15 km/hr,10 km/hr15 \mathrm{~km} / \mathrm{hr}, 10 \mathrm{~km} / \mathrm{hr}, and 8 km/hr8 \mathrm{~km} / \mathrm{hr}, respectively, how much distance in km will Ravi have run when Anil and Sunil meet again for the first time at the starting point?

Solution

✅ Correct Option: 3

They meet at the starting point only when both have completed whole laps at the same time.


Time for one complete lap using Distance ÷ Speed:

Anil:

315=15\dfrac{3}{15} = \dfrac{1}{5} hours per lap

Sunil:

310\dfrac{3}{10} hours per lap

Ravi:

38\dfrac{3}{8} hours per lap


To find when Anil and Sunil both finish whole laps together, we need the LCM of their lap times.

For fractions:

LCM(ab,cd)=LCM(a,c)GCD(b,d)\text{LCM}\left(\dfrac{a}{b}, \dfrac{c}{d}\right) = \dfrac{\text{LCM}(a,c)}{\text{GCD}(b,d)}

For 15\dfrac{1}{5} and 310\dfrac{3}{10}:

LCM(1,3)=3\text{LCM}(1,3) = 3 and GCD(5,10)=5\text{GCD}(5,10) = 5

Therefore:

LCM(15,310)=35\text{LCM}\left(\dfrac{1}{5}, \dfrac{3}{10}\right) = \dfrac{3}{5} hours


Ravi's distance in 35\dfrac{3}{5} hours:

Distance == Speed ×\times Time

=8×35=245=4.8= 8 \times \dfrac{3}{5} = \dfrac{24}{5} = 4.8 km


Answer: 4.84.8 km

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