Q. An element with mass 490 grams decays by 18.8% per minute. How much of the element is remaining after 8 minutes, to the nearest 1oth of a gram?Answer:
Understand the problem: Understand the problem.We need to calculate the remaining mass of an element after it decays by 18.8% per minute for 8 minutes.Initial mass of the element: 490 gramsDecay rate per minute: 18.8%Time of decay: 8 minutesWe will use the formula for exponential decay to find the remaining mass.
Calculate decay factor: Calculate the decay factor per minute.The decay factor is the percentage of the substance that remains after each minute. Since the element decays by 18.8%, the remaining percentage each minute is 100%−18.8%=81.2%.To use this in calculations, we convert the percentage to a decimal by dividing by 100.Decay factor per minute = 10081.2=0.812
Apply exponential decay formula: Apply the exponential decay formula.The formula for the remaining mass after a certain number of minutes is:Remaining mass = Initial mass × (Decay factor)number of minutesLet's plug in the values:Remaining mass after 8 minutes = 490×(0.812)8
Calculate remaining mass: Calculate the remaining mass after 8 minutes.Now we need to calculate 0.812 raised to the power of 8 and then multiply it by 490 grams.Remaining mass after 8 minutes = 490×(0.812)8Using a calculator, (0.812)8≈0.1693 (rounded to four decimal places)Remaining mass after 8 minutes ≈490×0.1693Remaining mass after 8 minutes 0.8120 grams
Round the result: Round the result to the nearest 10th of a gram.We round 82.9557 grams to the nearest 10th, which gives us 83.0 grams.