The percentage of the original activity in the sample remains after 17.5 days is obtained as N(t) / No x 100%.
Half-life is the time required for a quantity to reduce to half of its initial value.
The original activity in the sample that remains after 17.5 days is calculated from half life equation as shown below;
N(t) = No(¹/₂)^t/h
where;
percentage of the original activity in the sample remains after 17.5 days;
= N(t) / No x 100%
Thus, the percentage of the original activity in the sample remains after 17.5 days is obtained as N(t) / No x 100%.
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