Math Is Fun Forum

macy

Guest

Speed and distance

Please help me

Peter rides the bicycle at 10km/h from his home to the park at 10am. Half and hour later his sister
tries to catch him up at 12km/h. How long will it take her to meet him.

luca-deltodesco

Member

Registered: 2006-05-05

Posts: 1,470

Re: Speed and distance

moving at 10km/h, after 30 minutes Peter will have travelled 10*0.5 = 5km  (since 30minutes = 0.5hours)

at time t (hours), the sister will have moved 12t, whilst peter moves 10t, but peter is also 5km ahead of his sister

so you have the equation

12t = 5 + 10t
2t = 5
t = 2.5hrs

Last edited by luca-deltodesco (2009-07-01 22:33:55)

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Macy

Guest

Re: Speed and distance

thank you