Question

Erica and Amy started biking in the opposite directions at the same time from the same place. Erica biked at a speed of 6 meters per second and Amy biked at a speed of 4 meters per second. How soon were they exactly 1 km apart?

Answer 1

100 seconds

Erica and Amy are at distance of 1 km in 100 seconds

Explanation:

They both are travelling in opposite directions so the sum of the distances they travel is the distance between them.

Let's take t as the total time taken to achieve a seperation of 1km

Distance traveled by Erica , (Speed of Erica - v1)

x1 = v1 * t

Distance travelled by Amy , (Speed of Amy - v2)

x2 = v2*t

Therefore sum of the distances they traveled is x1+x2 = x

x = v1*t + v2*t

x = t*(v1 + v2)

Here it is given that final seperation between Amy and Erica is 1km or 1000 m

Therefore x = 1000 m

Thus t =
`(x)/(v1+v2)`

Substituting given values v1 = 6 m/s v2 = 4 m/s

Therefore,

They are apart by exactly 1km in a time of 100 sec