Question

The half-life of a certain radioactive material is 78 hours. An initial amount of the material has a mass of 790 kg.. Write an exponential function that models the decay of this material. Find how much radioactive material remains after. 18 hours. Round your answer to the nearest thousandth

Answer 1

 half life i= 78 hours 
 amount after 78 hours is 395 kg: 
395 = 790e^(k*78) 

Dividing by 790 and taking natural log
ln (395/790) = (k*78) 
-0.6931 = 78k 
-0.00888 = k  

lets calculate  how much is left after 18 hours: 
Amount(18)
= 790e^(-0.00888*18) 
Amount = 673.301 kg
hope this helps

Answer 2

Answer:

Step-by-step explanation:

For Lesson 3: Logarithmic Functions as Inverses Quiz Part 1

1. C) Graph with that starts along the negative x axis then goes up on the y axis on the positive x axis

2. A) Graph relatively does the same as the first one (for both 1 and 2, make sure that the negative x axis parts are on 0 y axis)

3. D) Also does the same, but starts along positive x axis, and still goes up.

4. B) Starts on negative x axis at -4 along y, going up to the y axis.

5. D) y=790(1/2)^1/78x; 673.233 kg

6. A) 4.9530

7. C) about 5.01 times as much energy

8. C) Graph goes up on the negative y axis, to the positive x axis and y axis.

9. A) Graph starts along the negative y axis, at -1 on the x axis, turning to the positive x axis and y axis.

Make sure to check if these answers match yours before using!!!