Example calculating radon-222 decay

Question

How many grams are left of 10 grams Rn-222 after 2 days
(half time of Rn-222 = 3.824 days).

Answer

Y = Y1*exp(-0.1815*X) Y1=initial mass of Rn-222 , X = days

Y = 10*exp(-0.1815*2) =**6.956** grams of Rn-222

Question

How many grams are left of 10 grams Rn-222 after 2 days

Answer

Y = Y1*exp(-0.1815*X) Y1=initial mass of Rn-222 , X = days

Y = 10*exp(-0.1815*2) =

Radon 222 half life curve. Screen shot from CHEMIX
School Curve fit & Function plot