Question

A radioactive element has half-life period of 30 days. How much of it will be left after 90 days?
A. `13.5%`
B. `46.5%`
C. `87.5%`
D. `90.15%`

Answer 1

Correct Answer - C
`90 "days" rarr 3 "half lives"`, left `1/8` i.e., `12.5%`
Disintegrated `= 100-12.5 = 87.5%`