Question

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Answer 1

Solution :

The relative velocity of the slow-moving train with respect to the boy is = (36 + 18)

km h^-1 = 54 km h^-1

= 54× $\dfrac{5}{18}$ m s^-1

= 15 ms^-1.

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Since the boy will watch the full length of the other train,

To find the time taken to watch the full train:

we have, 15 = [tex]\dfrac{90}{t}[/tex]

(or)

t = $\dfrac{90}{15}$

t = $\sf\dfrac{\cancel{90}}{\cancel{15}}$

$\boxed{\boxed{\bold{\therefore The\;time\;taken\;is = 6 s }}}$

Thank you for asking such an Valuable Question Mate.