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Two straight tracks AOB and COD meet each other at rt angles at point O.A person walking at a speed 55 km/hrkm/hr along AOB is at crossing O at 1212 o clock noon, another person with speed 55 km/hrkm/hr walking along COD reaches O at 11:3030 pm .F ind the time when the distance between the two persons is least?

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Apoorva , 10 Years ago
Grade 11
anser 1 Answer
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Saurabh Singh

Last Activity: 10 Years ago

at time t hours after 1:30


first person will be 7.5+5t from O
second person will be 5t from O

distance between two will be
7.5+5t^2 +5t^2
we need to minimize this
the plot would look like -->



179-428_MSP120920a0b008g4dh730c000035i9h49db4ih64aa.gif

so they are closest at 0.75 hours before 1:30
i.e 45 minutes before 1:30
i.e 12:45
nnnnnnnn

Thanks & Regards

n

Saurabh Singh,

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askIITians Faculty

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B.Tech.

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IIT Kanpur

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