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A girl of height 90 cm is walking awa...

A girl of height 90 cm is walking away from the base of a lamp-post at a speed of 1.2 m/s. If the lamp is 3.6 m above the ground, find the length of her shadow after 4 seconds.

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Let the girl of height be at point D on the ground from the lamp post after 4 seconds. Therefore,
AD=1.2 m/sec ×4 sec =4.8 m =480 cm
Suppose the length of the shadow of the girl be x cm when she at position D. Therefore,
BD=x cm
...
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