Help me with this Logarithmic Functions question if you can or want to.

If you decay at 25% per decade , then at the end of each decade you have 75% of what you started with at the beginning of the decade. So after n decades, the original amount gets multiplied by

.75^n

If t = number of years, then n = t/10, so after t years the original amount is multiplied by

.75^(t/10)

This is the same as

[.75^(1/10)]^t = .972^t

(Instead of dividing by 10, we take the tenth root.)

That is , at the end of each year, we have 97.2% of what we had at the start of the year.

So the annual decay rate is 1 - .972 = .028, or 2.8% per year.