You shine a flashlight on a puppet to
create a creepy shadow on the wall.
The flashlight is 18 inches from the
puppet, and the puppet is 87 inches
from the wall. The puppet is 12 inches
tall. How tall is the creepy shadow?
A) 58 in.

B) 64 in
C) 70 in.
D) 76 in

E) 80 in.

it 2

step-by-step explanation:

8^1/3=2

ending amount = beginning amount / (2^n)

where "n" = number of half-lives (or elapsed time / half-life)

ending amount = 50 mg / (2 ^10 / 5.3)

ending amount = 50 mg / (2 ^ 1.8867924528)

ending amount = 50 m / 3.6981210597

ending amount = 13.5203794557 mg

or about 13.5 mg remain

source: