Use this formula to find it [tex]amount \: left = starting \: amount \: {( \frac{1}{2})}^{ \frac{time \: gone}{half \: life} } [/tex] Starting amount = 40g Half life = 4 days Time gone = 12 days Amount left = 40 (1/2)^12/4 = 40 (1/2)^3 = 40 (1/8) = 5 grams
