Q. An element with mass 780 grams decays by 16.3% per minute. How much of the element is remaining after 16 minutes, to the nearest 10 th of a gram?
Identify values: Identify the initial amount, decay rate per minute, and total time.Initial amount a = 780 gramsDecay rate per minute r = 16.3%Total time t = 16 minutes
Convert to decimal: Convert the decay rate from a percentage to a decimal.To convert a percentage to a decimal, divide by 100.r=10016.3%=0.163
Determine decay factor: Determine the decay factor per minute. The decay factor is the amount by which the substance decreases each minute. Since it decays by 16.3%, it retains 100%−16.3%=83.7% of its mass each minute. Decay factor per minute = 1−r=1−0.163=0.837
Calculate remaining amount: Calculate the remaining amount of the element after 16 minutes.The formula for exponential decay is:remaining amount = initial amount × (decay factor)total timeSubstitute the known values into the formula:remaining amount =780×(0.837)16
Perform calculation: Perform the calculation.Use a calculator to compute the remaining amount:remaining amount = 780×(0.837)16remaining amount ≈780×0.0494 (rounded to 4 decimal places)remaining amount ≈38.532 (rounded to 3 decimal places)
Round to nearest tenth: Round the result to the nearest tenth of a gram.To round to the nearest tenth, look at the hundredths place. If it is 5 or more, round up; if it is less than 5, round down.remaining amount ≈38.5 grams (since the hundredths place is 3, we round down)
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