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# struggling with a logarithm revision question on radioactive decay: can anyone help? watch

1. kbkjbj
2. I literally just put 4e^-0.2t in my calculator
3. (Original post by Sam00)
The mass kg of a radio-active substance remaining in a sample t years after starting timing is given by theequation 'x = 4e^-0.2t'

a) What was the mass at the start ofthe timing?

b) Find the mass left after 5 years

So far I have only worked out some of (a) and got an answer of 3.275kg, which I think is incorrect
This is A level Chemistry right?
I've never done A level chemistry but could you do when t=0 to get an initial mass of 4kg...
I believe you could also make a graph.
4. Ahh it looks like chemistry, I'm doing my AS's atm so I'm not familiar. After checking the graph for the equation, I believe the answer to part b is 1.5kg.
5. (Original post by Sam00)
I literally just put 4e^-0.2t in my calculator
What is it with you making these threads and then deleting all your posts and editing your OP? Do you have a reason for it?

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