The half-life of a radioactive material is 3175 years. If there is 400 grams of the radioactive material today, when would there be 25 grams still radioactive?

12700 years will be required so that there be 25 gm still radioactive.

Step-by-step explanation:

The half-life of the radioactive material is 3175 years.

So, the 400 gm of radioactive material will become 200 gm in 3175 years.

Again, the remaining 200 gm of radioactive material will become 100 gm in another 3175 years.

Now, the remaining 100 gm of radioactive material will become 50 gm in another 3175 years.

Similarly, the remaining 50 gm of radioactive material will become 25 gm in another 3175 years.

Therefore, there are four 3175 years i. e. (4 * 3175) = 12700 years in total to become 25 gm of the radioactive material remaining from 400 gm of the same. (Answer)