Half life oa radioactive material is 6.93 days. After how many days `(19/20)` part of the sample will decay?

15/16 part of radioactive material decays in 10 days. After how many days 3/4 part of the material will decay? Find also the half life of the radioactive material.

Half life of a radioactive material is 3600 years. Calculate the decay constant.

The half-life period of a radioactive element is 140 days. After 560 days, what amount of 1 g of the element will be reduced?