Answer:
19.3 years
Explanation:
Given that the initial mass of a sample of Element X is 100 grams,
The formula is given as:
N(t) = No × (1/2) ^t/t½
Element X is a radioactive isotope such that every 30 years, its mass decreases by half.
N(t) = Mass after time (t)
No = Initial mass = 100 grams
t½ = Half life = 30 grams
N(t) = 100 × (1/2) ^t/30
How long would it be until the mass of the sample reached 64 grams, to the nearest tenth of a year?
This means we are to find the time
N(t) = 100 × (1/2) ^t/30
N(t) = 64 grams
64 = 100(1/2)^t/30
Divide both sides by 100
64/100 = 100(1/2)^t/30/100
0.64 = (1/2)^t/30
Take the Log of both sides
log 0.64 = log (1/2)^t/30
log 0.64 = t/30(1/2)
t = 19.315685693242 years
Approximately = 19.3 years