She runs at a constant speed of 4m/s. When Christopher realized what just happened, he followed her ten (10) seconds later at a constant speed of 5 m/s. They both went to the nearest comfort room that is 400 m away from the church. (a) How long will it take Christopher to overtake Jackie? (b) How far is Jackie from church when overtaken by Christopher?
Answers & Comments
Answer:
a. 40 seconds
b. 200 meters
Explanation:
let:
x - no. of seconds elapsed
using the formula:
Speed=distance/time
or distance=speed*time
to answer (a), equate the distance of Christopher and Jackie after x seconds
4(x+10)=5x, Christopher was late 10 seconds, so Jackie has 10 seconds headstart
4x+40=5x
5x-4x=40
x=40 seconds
to answer (b)
just substitute the answer of (a) to any the two distances
x=40
4(x+10)=4(40+10)=4(50)=200 meters
or
5x=5(40)=200 meters