The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 210 grams of a radioactive isotope, how much will be left after 5 half-lives?

Question

anonymous · Answer

@FaiqRaees

faiqraees · Answer

So at each half life the mass gets halved
1st halflife = 210/2 g
2nd halflife = 105/2 g
3rd halflife = 52.5/2 g
4th halflife = 26.25/2 g
5th halflife = 13.125/2 g = 6.5625 g

anonymous · Answer

Wait .. What? So how would i answer the question ? Is there a formula ...

faiqraees · Answer

You can even use the formula to calculate it
Amount left = Initial *(1-rate)^halflife

anonymous · Answer

so would it look like 210 * ( 1 - ? )^5

anonymous · Answer

I am not sure what goes where the rate is

faiqraees · Answer

Everytime the mass gets halved
Which means the mass gets multiplied by 0.5
So the rate here is 0.5

anonymous · Answer

Okay so 
210 * ( 1 - 0.5) ^5

faiqraees · Answer

yes

anonymous · Answer

I got 6.5625 
Is that right ?

faiqraees · Answer

correct

anonymous · Answer

Oh my goodness ! Thank you ! :)