Question

2/3 fraction of a sample disintegrates in 7 days. how much fraction of it will decay kn 21 days.​

Answer 1

Answer:

26/27 fraction of sample will decay in 21 days.

Explanation:

In every 7 days, 2/3rd fraction of sample disintegrates.

Let the sample quantity = X

In 1st 7 days, 2/3 will get integrate.

Remaining sample = 1/3 X

In next 7 days, 2/3rd of the remaining sample will get disintegrate.

∴ Remaining sample after 14 days = 1/3X - (2/3)×(1/3)X = 1/9X

After 21 days futher 2/3 will get disintegrate of the remaining.

∴ After 21 days, remaining sample = (1/9)X - (2/3)× (1/9) X

∴ Final remaining sample = (1/27)X

∴ Sample Disintegrated = X - 1/27X = 26/27X