Brown starts 2 hours after John and overtakes him in 4 hours. If the difference between the speeds of John and Brown is 20 kmph, what is the distance travelled by Brown before meeting John?

Let Brown's speed be v kmph, making John's speed (v - 20) kmph. When Brown travels for 4 hours, John travels for 6 hours because he started 2 hours earlier. Equating their distances gives 4v = 6(v - 20), which solves to v = 60 kmph. The distance travelled by Brown is 60 kmph times 4 hours, which equals 240 km. The result is 240 km.

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