Wednesday

July 30, 2014

July 30, 2014

Posted by **kela** on Friday, November 9, 2012 at 6:00pm.

(a) What is the half-life of the substance?

(b) How long would it take the sample to decay to 65% of its original amount?

- calculus -
**Reiny**, Friday, November 9, 2012 at 6:06pmgeneral equation

amount = starting (1/2)^(t/k) , where t is the time and k is the half-life period

a)

.945 = 1(.5)^1/k

ln .945 = (1/k)ln.5

1/k = ln.945/ln.5

k = ln.5/ln.945 = 12.25 years

b)

.65 = (.5)^t/12.25

t/12.25 = ln.65/ln.5 = .621488..

t = 7.61 years

- calculus -
**Anonymous**, Friday, March 7, 2014 at 3:08amA certain radioactive isotope decays at a rate of 2% per 100 years. If t represents time in years and y

represents the amount of the isotope left then the equation for the situation is y= y0e-0.0002t. In how many years will there be 93% of the isotope left?

**Related Questions**

Calc - A sample of a radioactive substance decayed to 93.5% of its original ...

calculus - The rate at which an amount of a radioactive substance decays is ...

Science - Radioactive substance decays so that after t years, the amount ...

Calculus-derivatives - Verify if these are correct answers. 1. The derivative of...

Math/Calculus - After 5 days, a particular radioactive substance decays to 37% ...

Math - A radioactive substance decays according to the formula Q(t) = Q0e−...

Math - A radioactive substance decays according to the formula Q(t) = Q0e−...

Math - Phosphorus-32 (P-32) has a half-life of 14.2 days. If 200 g of this ...

math - Phosphorus-32 (P-32) has a half-life of 14.2 days. If 200 g of this ...

Math - Phosphorus-32 (P-32) has a half-life of 14.2 days. If 200 g of this ...