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Answer:
x = 18.
Step-by-step explanation:
x + 9.5 = 27.5
Subtract 9.5 from both sides:
x = 27.5 - 9.5
x = 18 (answer).
Answer:
Answer is 60%
Step-by-step explanation:
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Answer:
a) Two half lives, b) 
Step-by-step explanation:
a) The polonium-210 has a half life of 138.4 days. Therefore, 1.994 half lives have past.
b) Mass decay is described by the following exponential model:

The time constant for the isotope is:


The mass of the isotope after 276 days is:

