Answer: approximately 27 grams
Work Shown:
Half life formula
y = A*(0.5)^(x/H)
where,
- A = starting amount = 30 grams
- H = half life period = 90 years
- x = number of years that pass by = 12
- y = amount left over after x years
Let's plug the values for x, A and H into the formula to find y
y = A*(0.5)^(x/H)
y = 30*(0.5)^(12/90)
y = 27.3516746567466
y = 27 .... rounding to the nearest whole number