Any one knows how to do this physics question?

Question

Radioactive disintegration of some kernel occurs under the scheme:
X ----> 2 α 4 + 84 Po 218
Find the activity of element X in 11,4 day after the beginning of disintegration.
(use sub and superscript beside of α and Po)

Answer 1

Use the standard formula.

A = Ao x exp (-lambda x time)

Ao = initial value of activity
lambda = decay constant = ln(2) / half life.

A thumbs DOWN? !!! Next time I think I'll give the wrong answer. Or am I expected to do the whole thing rather than tell you HOW to do it?

Answer 2

Element X is Radon, 222Rn which has a half-life of 3.8 days. So after 3 half-life periods, (3.8*3 = 11.4) you will have 1/8 of the original amount of Radon. 1/2 * 1/2 *1/2 = 1/8

So if you had 8 pounds of Radon, after 11.4 days, you only have 1 pound left. The rest has become Polonium (Po)...and then decays into something else.