Two trains on opposite tracks leave the same station at the same time. One train travels at an average speed of 80 kilometres per hour and the other travels at an average speed of 70 kilometres per hour. How long after they leave the station will they be 50 km apart?

9514 1404 393

  20 minutes

Step-by-step explanation:

The trains are separating at the rate of 80 +70 = 150 km/hour. The time required to be 50 km apart is then ...

  time = distance/speed = (50 km)/(150 km/h) = 1/3 h = 20 minutes

f

step-by-step explanation:

f

x =±sqrt(1/3)

step-by-step explanation:

x+4/6x=1/x

multiply each side by 6x to get rid of the fractions

6x*(x+4/6x)=1/x*6x

distribute

6x^2 +4 = 6

subtract 4 from each side

6x^2 +4-4 = 6-4

6x^2 =2

divide by 6

6x^2/6 = 2/6

x^2 = 1/3

take the square root of each side

sqrt(x^2) = ±sqrt(1/3)

x =±sqrt(1/3)