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An element with a mass of 220 grams decays by 
26.6% per minute. To the nearest tenth of a minute, how long will it be until there are 10 grams of the element remaining?
Answer:

An element with a mass of 220220 grams decays by 26.6% 26.6 \% per minute. To the nearest tenth of a 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 220220 grams decays by 26.6% 26.6 \% per minute. To the nearest tenth of a minute, how long will it be until there are 1010 grams of the element remaining?\newlineAnswer:
  1. Understand the decay process: Understand the decay process.\newlineThe decay process can be described by the exponential decay formula: N(t)=N0×(1r)tN(t) = N_0 \times (1 - r)^t, where N(t)N(t) is the remaining amount after time tt, N0N_0 is the initial amount, rr is the decay rate per time period, and tt is the time period.
  2. Convert to decimal: Convert the percentage decay rate to a decimal.\newline26.6%26.6\% as a decimal is 0.2660.266.
  3. Set up equation: Set up the equation with the given values.\newlineWe have N0=220N_0 = 220 grams, N(t)=10N(t) = 10 grams, and r=0.266r = 0.266. Plugging these into the decay formula gives us 10=220×(10.266)t10 = 220 \times (1 - 0.266)^t.
  4. Simplify the equation: Simplify the equation.\newlineDivide both sides by 220220 to isolate the exponential expression: 10220=(10.266)t\frac{10}{220} = (1 - 0.266)^t.
  5. Calculate left side: Calculate the left side of the equation. 10220\frac{10}{220} simplifies to 122.\frac{1}{22}.
  6. Take natural logarithm: Take the natural logarithm of both sides to solve for tt.ln(122)=ln((10.266)t)\ln(\frac{1}{22}) = \ln((1 - 0.266)^t).
  7. Use logarithm property: Use the property of logarithms to bring down the exponent.\newlineln(122)=t×ln(10.266)\ln(\frac{1}{22}) = t \times \ln(1 - 0.266).
  8. Calculate ln values: Calculate ln(10.266)\ln(1 - 0.266) and ln(122)\ln(\frac{1}{22}).\newlineln(10.266)ln(0.734)\ln(1 - 0.266) \approx \ln(0.734) and ln(122)ln(0.04545)\ln(\frac{1}{22}) \approx \ln(0.04545).
  9. Divide to solve: Divide to solve for tt.t=ln(0.04545)ln(0.734)t = \frac{\ln(0.04545)}{\ln(0.734)}.
  10. Calculate t value: Calculate the value of tt.tln(0.04545)/ln(0.734)3.09104/0.309529.987t \approx \ln(0.04545) / \ln(0.734) \approx -3.09104 / -0.30952 \approx 9.987, which rounds to 10.010.0 to the nearest tenth of a minute.

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