A point source of light along a straight road is at a height of ‘a’ metres. A boy ‘b’ metres in height is walking along the road. How fast is his shadow increasing if he is walking away from the light at the rate of c metres per minute?
Let AB = a metres be the lamp-post and PQ = b metres the boy, CP = y be his shadow at time t. Let AP = x.
Now ∆CAB and ∆CPQ are equiangular and hence similar
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