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An element with a mass of 910 grams decays by 
27.4% per minute. To the nearest minute, how long will it be until there are 10 grams of the element remaining?
Answer:

An element with a mass of 910910 grams decays by 27.4% 27.4 \% per minute. To the nearest minute, how long will it be until there are 1010 grams of the element remaining?\newlineAnswer:

Full solution

Q. An element with a mass of 910910 grams decays by 27.4% 27.4 \% per minute. To the nearest minute, how long will it be until there are 1010 grams of the element remaining?\newlineAnswer:
  1. Identify amounts and rate: Identify the initial amount, final amount, and the decay rate per minute.\newlineInitial amount aa = 910910 grams\newlineFinal amount yy = 1010 grams\newlineDecay rate per minute = 27.4%27.4\%
  2. Convert rate to decimal: Convert the decay rate from a percentage to a decimal for calculation purposes.\newlineDecay rate per minute = 27.4%=27.4100=0.27427.4\% = \frac{27.4}{100} = 0.274
  3. Use exponential decay formula: Use the exponential decay formula y=a×(1r)ty = a \times (1 - r)^t, where yy is the final amount, aa is the initial amount, rr is the decay rate, and tt is the time in minutes.\newlineWe need to solve for tt when y=10y = 10 grams, a=910a = 910 grams, and r=0.274r = 0.274.\newline10=910×(10.274)t10 = 910 \times (1 - 0.274)^t
  4. Isolate exponential part: Divide both sides of the equation by 910910 to isolate the exponential part of the equation.\newline10910=(10.274)t \frac{10}{910} = (1 - 0.274)^t
  5. Simplify left side: Simplify the left side of the equation.\newline109100.01098901\frac{10}{910} \approx 0.01098901\newline0.01098901=(10.274)t0.01098901 = (1 - 0.274)^t
  6. Take natural logarithm: Take the natural logarithm (ln\ln) of both sides to solve for tt.ln(0.01098901)=ln((10.274)t)\ln(0.01098901) = \ln((1 - 0.274)^t)
  7. Bring down exponent: Use the property of logarithms that ln(ab)=b×ln(a)\ln(a^b) = b \times \ln(a) to bring down the exponent tt.ln(0.01098901)=t×ln(10.274)\ln(0.01098901) = t \times \ln(1 - 0.274)
  8. Calculate logarithms: Calculate ln(10.274)\ln(1 - 0.274) and ln(0.01098901)\ln(0.01098901) using a calculator.\newlineln(10.274)ln(0.726)0.319\ln(1 - 0.274) \approx \ln(0.726) \approx -0.319\newlineln(0.01098901)4.512\ln(0.01098901) \approx -4.512
  9. Solve for t: Divide both sides of the equation by ln(10.274)\ln(1 - 0.274) to solve for t.t=ln(0.01098901)ln(10.274)t = \frac{\ln(0.01098901)}{\ln(1 - 0.274)}t4.5120.319t \approx \frac{-4.512}{-0.319}
  10. Round to nearest minute: Calculate the value of tt using the values from the previous step.\newlinet4.512/0.319t \approx -4.512 / -0.319\newlinet14.144t \approx 14.144
  11. Round to nearest minute: Calculate the value of tt using the values from the previous step.t4.5120.319t \approx \frac{-4.512}{-0.319}t14.144t \approx 14.144Since we cannot have a fraction of a minute in this context, we round tt to the nearest whole minute.t14t \approx 14 minutes

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