Pre-cal homework help not just answer but how to do it too  TOPIC_SOLVED

Complex numbers, rational functions, logarithms, sequences and series, matrix operations, etc.

Pre-cal homework help not just answer but how to do it too  TOPIC_SOLVED

Postby AlejandroDeLaPreCal on Wed Mar 19, 2014 12:32 am

This exercise uses the radioactive decay model.

The half-life of cesium-137 is 30 years. Suppose we have a 128-g sample.

(a) Find a function that models the mass remaining after t years. (Round rate r to three significant figures.)


(b) How much of the sample will remain after 120 years? (Round your answer to one decimal place.)
g


(c) After how long will only 4 g of the sample remain? (Round your answer to the nearest whole number.)
yr
AlejandroDeLaPreCal
 
Posts: 1
Joined: Wed Mar 19, 2014 12:29 am

Sponsor

Sponsor
 

Re: Pre-cal homework help not just answer but how to do it t

Postby anonmeans on Wed Mar 19, 2014 11:58 am

AlejandroDeLaPreCal wrote:This exercise uses the radioactive decay model.

To see how to do this, try this page.

AlejandroDeLaPreCal wrote:The half-life of cesium-137 is 30 years. Suppose we have a 128-g sample.

So P = 128.

AlejandroDeLaPreCal wrote:(a) Find a function that models the mass remaining after t years. (Round rate r to three significant figures.)

What is half of 128? This is A. This is how much you have at t = 30. Plug these into the equation (A = Pe^{rt}) and solve for r.

AlejandroDeLaPreCal wrote:(b) How much of the sample will remain after 120 years? (Round your answer to one decimal place.)

Use the P they gave you, the r you just found, and the t they give you for this part. Plug them into the equation and solve for A.

AlejandroDeLaPreCal wrote:(c) After how long will only 4 g of the sample remain? (Round your answer to the nearest whole number.)

Use the P they gave you, the r you found, and the A they give you for this part. Plug them in and solve for t.

If you get stuck, please write back showing what you've done. Thanks.
anonmeans
 
Posts: 52
Joined: Sat Jan 24, 2009 7:18 pm


Return to Advanced Algebra ("pre-calculus")

cron