# ap calculus

suppose that the amount in grams of a radioactive substance present at time t (in years) is given by A (t) = 160e-.70t. Find the rate of decay of the quantity present at the time when t = 4

1. 👍
2. 👎
3. 👁
1. A ' (t) = -.7(160) e^(-.7t)

so A ' (4) = -.7(160) e^-2.8
= -6.81

insert the units

1. 👍
2. 👎

## Similar Questions

1. ### calculus

A sample of a radioactive substance decayed to 94.5% of its original amount after a year. (Round your answers to two decimal places.) (a) What is the half-life of the substance? (b) How long would it take the sample to decay to

2. ### Calc

A sample of a radioactive substance decayed to 93.5% of its original amount after a year. a) What is the half-life of the substance? ? years (b) How long would it take the sample to decay to 10% of its original amount? ? years

3. ### URGENT! Due soon and I used 8 of 10 attempts

Archaeologists can determine the age of artifacts made of wood or bone by measuring the amount of the radioactive isotope 14C present in the object. The amount of isotope decreases in a first-order process. If 14.5% of the

4. ### Exponential Modeling

The half-life of a radioactive substance is one day, meaning that every day half of the substance has decayed. Suppose you have 100 grams of this substance. How many grams of the substance would be left after a week?

1. ### Calculus

[Exponential growth & decay] The half-life of radioactive strontium-90 is approximately 29 years. In 1965, radioactive strontium-90 was released into the atmosphere during testing of nuclear weapons, and was absorbed into people's

2. ### precal

If the half-life of a certain radioactive substance is 2000 years, estimate how many years must elapse before only 35% of the radioactive substance remains?

3. ### Algebra

If 18g of a radioactive substance are present initially and 8 yr later only 9 g remain, how much of the substance will be present after 20 yr?

4. ### math

The exponential function N = 500 × 0.74t, where t is measured in years, shows the amount, in grams, of a certain radioactive substance present. What is the monthly percentage decay rate? (Round your answer to one decimal place.)

1. ### Math

A radioactive substance decays according to the formula Q(t) = Q0e−kt where Q(t) denotes the amount of the substance present at time t (measured in years), Q0 denotes the amount of the substance present initially, and k (a

2. ### algebra

A radioactive substance decays according to the formula A=A0e^kt where A0 is the initial amount of substance (in grams) A is the amount of substance(in grams) after t years k is a constant The half-life of the substance is 10

3. ### Physical Science- Help Please!

Suppose that you are given a 100 gram sample of a radioactive substance with a half-life of 32 days. How many grams will be left after 192 days?

4. ### Chem

According to the Arrhenius Theory of acids and bases, a base is: A A substance that decrease the amount of hydroxide ions present. B A substance that increases the amount of hydroxide ions present when it is dissolved in water. C