Percentage transmittance gamma ray through lead

[Adam Rabe]

Homework Statement

Homework Equations

I = Io e^-ux

The Attempt at a Solution

0.75 = 1 * e^-u1
using algebra... u =2.117

I = 1 * e^-2.117*3
I = 0.00175

Answer is apparently 42.2. Can someone tell me where i went wrong? Thanks for any help as always

 

[Drakkith]

0.75 = 1 * e^-u1
using algebra... u =2.117

Check your math. When I put $e^{-2.117}$ into my calculator, I don't get 0.75.

 

[Adam Rabe]

Check your math. When I put $e^{-2.117}$ into my calculator, I don't get 0.75.

omfg i got it. thanks a lot i derped out with the log rules.