if denny has already walked 1800 m, how many minutes will it take for John to catch up with Denny by bike assuming Denny continues to walk?

Question

denny walk 60 m in 1 minute, and John travels 210m in 1 minute by bike.

Answer 1

For Denny

d = 1800 + rt

d = 1800 + 60t

 

For John

d = rt

d = 120t

 

Both travel the same distance

 

1800 + 60t = 120t        subtract 60t from both sides

1800 = 150t                  divide both sides by 150

12 = t

 

John catches up in 12 minutes.

 

Answer 2

Hi Xixi,

I now realize I answered this for you earlier INCORRECTLY

John has to close an 1800 m head start.
time = distance/rate

time = 1800 m / (210 m/min - 60 m/min)

(We adjust the rate that John gains on Denny here because they are both moving)

time = 1800/150 = 12 min.