The count rate meter is used to measure that activity of a given amount of a radio active element. At one instant, the meter shows 475 counts/minute. Exactly 5 minutes later, is shown 270 counts/minute then
The decay constant is

Options

A. 0.82/minute
B. 0.113/minute
C. 0.166/minute
D. 0.182/minute

Answer

B

Explanation

`A=A_(0)e^(-lambda t), 270=475 e^(-lambda t)`
On solving we get `lambda = 0.113// min`