Half-life is defined as the amount of time it takes a given quantity to decrease to half of its initial value. The equation to describe the decay is
Nt=N0(1/2)

where N0 is the initial quantity, Nt is the remaining quantity after time t, t1/2 is the half-time. So work out the equation, t1/2 = t (-ln2)/ln(Nt/N0) = 11.5*(-ln2)/ln(12.5/100) = 3.83 days
Basic facts about sex and reproduction, as told to a child
Answer:
All the numbers in a chemical formula are significant, It is because the numbers in a chemical formula denote the number of different atoms present in the particular compound.
For example in H2SO4 there are 2 H 1 S and 4 O. This means 1 H2SO4 has 2 hydrogen 1 sulphur and 4 oxygen.
Always use this method !!! always