You received a shipment 20 days ago of 13 i for treatment of hyperthyroidism. what fraction of the original shipment would you still have with a half-life of 8.040 days for 31?

we will have 17.8 % of the original value

Explanation:

As we know that by radioactive decay the total number of nuclei present at any instant of time is given as

here we need to find the fraction of total number of nuclei present

so we will have

so we have

now we have

so we will have 17.8 % of the original value

b. a lightning bug, plug of grass, and a worm

total distance/total time

(85 + 82)/(5+3)

167/8

20 just over