What is the half life of a radioisotope if you started with 1 gram and 0.250 grams is left after 6 days?

3 days

Explanation:

We have to use the formula;

N/No = (1/2) ^ t/t1/2

Where;

N = amount of radioactive material left after a time t = 0.250g

No = original amount of radioactive substance present = 1g

t = time taken to decay to N = 6 days

t1/2 = half life of the sample

N/No = (1/2) ^ t/t1/2

Substituting values;

0.25/1 = (1/2) ^6/t1/2

25/100 = (1/2) ^6/t1/2

1/4 = (1/2) 6/t1/2

(1/2) ^2 = (1/2) 6/t1/2

Canceling out bases and equating powers

2 = 6/t1/2

t1/2 = 6/2

t1/2 = 3 days