Help! F.1 maths question

Question

Peter and Mary run with speed 1.2m/s and 4 km/h respectively.

If the track is 400m long,how long does Peter take to overlap Mary?

Answer 1

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Do such question, normally you set Y be the answer you want to find,

here, i.e., the time take for Peter to overlap Mary (Y in second)

Then form the equation:

(When Peter ran 400m far from Mary, then he overlap)

1.2m/s x Y = 4km/h x Y + 400

resolve all unit to meter

1.2Y = (4000/3600)Y + 400

Y = 4500

So it take 4500 seconds to overlap Mary

(or 75 minutes)

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