Strontium-85 has a half-life of 65 days. how long will it take for the radiation level of strontium-85 to drop to one-fourth of its original level?

130 days

Explanation:

Strontium-85 has a half-life of 65 days. how long will it take for the radiation level of strontium-85 to drop to one-fourth of its original level?

Strontium-85 is a radioactive element. so it takes 65days for one strontium of a particular mass to decrease to half of its initial size

Half life  is the time taken for a radioactive element to decrease to half of its initial size. it decays by half every 65 days.

from 1 to 1/2  = 65 days

from 1/2 to 1/4  =65 days

from 1/4 to 1/8 = 65 days

from 1/8 to 1/16 = 65 days

total time taken to decay from original amount to 1/4 is two half lives =

65+65=130 days

305.7

explanation:

density =m/v

density =917/3.00

density = 305.

approximately = 305.7

in four significant figures