A load requirement in your plan is 60 psf at a joist spacing of 16 inches. If the room dimensions are length 13 feet 2 inches and width 11 feet 7 inches, are 2 X 10 boards appropriate?

answer: the correct answer is -32

step-by-step explanation:

ending amount = beginning amount / (2^n)

where "n" = number of half-lives (or elapsed time / half-life)

ending amount = 50 mg / (2 ^10 / 5.3)

ending amount = 50 mg / (2 ^ 1.8867924528)

ending amount = 50 m / 3.6981210597

ending amount = 13.5203794557 mg

or about 13.5 mg remain

source: