Usha particpated in a marathon walk and completes the journey in 10 h. if she travels half the distance with a speed of `10 km h^(-1)` and rest of the distance with the speed of `15 km h^(-1)` then calculate the total distance of the marathon walk.

Explanation

Let the total distance be x km
speed = `("distance")/("time")`
` "Time"= ("distance")/("speed")`
` t_(1) = x/(2 xx 10) = x/20`
` t_(2) = (x / (2xx 15) = x/30 , t_(1) + t_(2) = 10 ` hours
` x/20 + x/30 = 10 `
30x + 20x = 6000
50x = 6000,x x=120 km