Question

A girl of height 90cm walks away from the foot of a lamp post at 1.2m/s. If the
lamp is at a height of 3.6m from the ground find the length of shadow of gir
after 4 seconds.​

Answer 1

Suppose the length of the shadow of the girl be x cm when she at position D. Therefore,

BD=x cm

In ∆BDE and ∆BAC,

∠BDE=∠BAC (90°)

∠DBE=∠ABC (Common)

Thus, ∆BDE∼∆BAC (AA similarity)

BC

BE

=

AC

DE

=

AB

BD

( Corresponding sides are proportional )

360

90

=

480+x

x

⇒

4

1

=

480+x

x

⇒4x=480+x

⇒4x−x=480

⇒3x=480

⇒x=

3

480

=160

Hence length of her shadow after 4 seconds is 160 cm.

solution

Hope this helps you out.

I can't understand Kannada but I can understand maths. :)

peace out. Thank you