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Question

Hi,

need help on this question :

 

Mr Lee took 6hrs to drive from Town X to Town Y while Mdm Ong took 4 hrs to drive from Town Y to Town X. Both of them started driving at 9am. What time did the two of them pass each other ?

Answer

Consider distance as 1 unit

Mdm Ong speed = 1/4
Lee speed = 1/6

Since they are opposing direction, relative speed is a sum of both speed.
Relative speed = 1/4 + 1/6 = 10/24

Time = distance/speed = 1/(10/24) = 2.4 hours or 2hrs and 24mins

Time they meet = 11:24am

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Thanks both !!

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post-16648

It is clear Mdm Ong is traveling at 6/4 = 3/2 = 1.5 times faster than Mr Lee.

Let S be the speed that Mr Lee is travelling.

Let D be the distance between Town X and Town Y

Let T be the time taken for both Mr Lee and Mdm Ong to meet.

D = 6S

D = ST+1.5ST = 2.5ST

Hence 2.5ST = 6S

=> T= 6/2.5 = 2.4hrs

So they will meet at 9am + 2.4hrs = 11:24am

 

 

 

 

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