"What is the half-life of a radioactive substance that has a decay rate of 25% per decade?
Hint: Remember that the Rule of 70 does not give a good approximation to half-life when the rate is larger than 15%. We must use the actual formula here."
This what I did.
I used the exact half-life formula:
In this case, r= 0.25
After substituting, I get:
0.301030 = -2.4094
Am I right? I'm a bit confused..