Answer:
226 grams
Explanation:
The half-life of a radioactive substance is the time taken for half the quantity of the substance to decay such that the amount life after the given period of time is half the original quantity.
As such, given that the half-life of a certain radioactive element is 35 hours and there are 904 grams available, it means that after 35 hours,
Amount decayed = 1/2 * 904 grams
= 452 grams
Amount left = 904 grams - 452 grams
= 452 grams
After another 35 hours (now a total of 70 hours),
Amount decayed = 1/2 * 452 grams
= 226 grams
Amount left = 452 grams - 226 grams
= 226 grams