Unstable substance exhibity higher radioactivity due to

Radioactivity is due to

Radioactive is due to

Radioactivity is due to

Radioactivity is due to

Radioactivity is due to

Radioactivity is due to

Radioactivity is due to

If 20 gm of a radioactive substance due to radioactive decay reduces to 10 gm in 4 minutes, then in what time 80 gm of the same substance will reduce to 10 gm-