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Half-life Answer Sheet (Okay, I made a mistake. I put a plus where a “x” went in the formula. Remember I have been sick and I am losing my mind.) For the first problem divide B/E first and then take log. For second problem make sure to put the 20/14 in parentheses. Rounding will change numbers considerably. 1. H= T x log 2 Log B/E 14= (T x log 2) / Log (10,000/8500) 14= T x .30 .0701 .988/.30=T 3.29 days = T 2. Y=A x ½ ^t/h Y= 10,000 x ½ ^ (24/14) Y= 10,000 x (.3048) Y= 3048 cpm 3. 20= T x log 2 Log 10,000/4000 20= (T x .30)/ .39794 7.9588 / .30= T 26.52 days = T 4. Y= 10000 x ½ ^ (t/h) Y= 10000 x ½ ^ (10/14) Y= 10000 x (.6095) Y= 6095 cpm 5. 330= (T x .30)/log (20,000/100) 330= (T x .30) / 2.301 330 x 2.301 = T x .30 759.34 / .30= T 2531 days = T 330= (T x .30) / log (20000/ 50) 330= (T x .30)/ 2.6021 858.68 / .30 = T 2862 days = T 6. Y = 3000 x ½ ^(60/24) Y = 3000 x 0.17678 Y= 530 cpm 7. Y=400 x .5 ^ (24/8) Y= 400 x 0.125 Y= 50 Iodine left So that means 350g of Xe 8. 5730= (T x log 2)/ log (14/ 8) 5730= (T x .30) / 0.2430 1,392.39/.30 = T 4,642 years = T 9. Y= 10,000 x ½ ^ (100/45) Y= 10,000 x 0.2143 Y= 2,143 cps 10. 45= T x .30/ log (10,000/4000) 45 x .3979= T x .30 17.91/ .30 = T 59.7 days 11. 5730= (T x .30)/ log (15.7/ 11.76g) 5730= (T x .30)/ 0.1255 5730 x 0.1255= T x .30 719. 12 / .30= T 2,397years He was found in 1950 so his initial activity started in 447 BC and he was 45 when he died so 402 BC.