Radium-223 id a radioactive isotope with a half-life of 11.4 days. approximately how long will it take for the activity of a sample 223ra to decease to 2.50% of its initial value

It will take 61 days for the activity of a sample Ra-223 to decease to 2.50% of its initial mass.

Explanation:

Initial mass of the Radium-223= x

Final mass of the Radium-223 left after time t = 2.50% of x= 0.025x

Time taken by the sample = t

Half life of the Radium-223 =

Formula used :

where,

= initial mass of isotope

N = mass of the parent isotope left after the time, (t)

= half life of the isotope

= rate constant

It will take 61 days for the activity of a sample Ra-223 to decease to 2.50% of its initial mass.

what is the general relationship between a galaxy's distance from earth and its speed?

the answer is:

the farther away a galaxy is from us, the faster it is moving away from us.