Answer:
Length of her shadow after 4 second is 160 cm
Explanation:
Let the girl be at point D on the ground from the lamppost after 4 sec.
BD = 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.
ED = x cm
In ∆EDC and ∆EBA
∠EDC = ∠EBA (90°)
∠DEC = ∠BEA (Common)
∆EDC ∼ ∆EBA (AA similarity)
EC/EA = DC/BA = ED/BE
EC/EA = ED/BE
90cm/360cm = x cm/(480+x) cm
1/4 = x/x+480
4x = x + 480
3x = 480
x = 480/3
x = 160
(corresponding sides or proportional)
So, the length of her shadow after 4 second is 160 cm.
