A radioactive isotope has a life for 15 minutes. It has an initial count rate of 36000 Bg. What will the count be after 1 hour?

18000 Bg

Explanation:

after 15 minutes = 36000/2

After 30 minutes = 36000/4

30 minutes × 2 = 1 hour

After 1 hour = 36000/4 × 2 = 18000 Bg

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west