How much was present at the original measurement?

Question

I also need to know how much was in the sample to the nearest gram after 4hrs. based on the above information

 

a sample of radioctive substance decayed according to y=210(10)^-3x where y was the mass in grams and x was the time in hours after the original measurement.

Answer 1

At the original measurement, x = 0 since zero hours have passed. So, plug in x = 0 and solve for y:

 

y = 210(10)^-3(0)

y = 210(10)⁰

y = 210(1)

y = 210

 

There were 210 grams initially.

 

 

After four hours, x = 4. So, plug in x = 4 and solve for y. You'll get a very small number.