5/3if 87.5 percent of a sample of pure 131 i decays in 24 days, what is the half-life of 131 i?

1st time of decay: 50%

2nd time of decay: 50%+25%=75%

3rd time of decay: 75+12.5%=87.5%

Therefore, 87.5% of the samples decays in 3 half-lives

Therefore, 24 days is 3 half-lives

Therefore:

1 half-life is 24/3 = 8 days