0.25 mg / 8 = 0.031 mg (2 significant figures).
Amount of chromium-51 remaining after 83.1 days = 0.031 mg
Radioactive disintegration follows the exponential law which can be mathematically expressed as:
where N(0) = initial amount of the radioactive substance
N(t): radioactive substance left after time t
t1/2 = half life of the radioisotope
In the case of chromium-51:
N(0) = 0.25 mg
t = 83.1 days
t1/2 = 27.7 days
Substituting these values in equation (1) gives:
i think its 100
i hope this !