Question

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

Answer 1

Step-by-step explanation:

Given, speed=1.2m/sec

time=4sec

speed=

time

distance

1.2=

4

distance

distance=AD=12×4=4.8m

Consider △ABC and △DBE

∠CAB=∠EDB=90

∘

∠CBA=∠EDB (common angle)

So by AA, △ABC∼△DBE

Hence

DE

AC

=

DB

AB

DE

AC

=

DB

AD+DB

0.9

3.6

=

DB

4.8+DB

4DB=4.8+DB

3DB=4.8

DB=1.6

Hence the length of the shadow 1.6m