# Triangle

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.

[email_link] http://solvemaths.in/triangle/GeometryA 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.

dinesh
ppboomshankar@gmail.comSubscriberSOLVE - ΜΔΓΗŠ
Let AB be the lamp-post and CD the girl after walking for 4 seconds.

Let DE be x metres.

NOW,

BD = 1.2×4=4.8 m

Note that in triangle ABE and triangle CDE ,

<B =<D ( EACH IS 9O

and <E = <E (A-A similarity critection

so, tri ABC = tri CDE

Therefore,

BE/DE = AB/CD

I.E 4.8+X/X = 3.6/O.9

4.8+X/X = 4

4.8+ X = 4x

3x= 4.8

X= 1.6

So, the shadow of the girl after walking for 4 seconds is 1.6 m long.