Half-Life of Strontium-90 - Solve Here!

[cowboi123]

Homework Statement

The half life of strontium-90 is 28.0 years. Deduce that the decay constant of strontium-90 is 7.85 * 10^(-10) s^1.

Homework Equations

k = ln 2 over half-life in seconds

The Attempt at a Solution

dunno...please help me solve this!

 

[Dick]

Well, express 28 years in seconds and divide log(2) by that? I don't know what else to say.