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Beginning with 29 grams of a radioactive element whose half-life is 45 years, the mass [tex]\( y \)[/tex] (in grams) remaining after [tex]\( t \)[/tex] years is given by

[tex]\[ y = 29 \left(\frac{1}{2}\right)^{t / 45}, \quad t \geq 0. \][/tex]

How much of the initial mass remains after 150 years? (Round your answer to three decimal places.)


Sagot :

Certainly! Let's calculate the mass of the radioactive element that remains after 150 years, given the half-life of 45 years and an initial mass of 29 grams. The formula to determine the remaining mass [tex]\( y \)[/tex] after [tex]\( t \)[/tex] years is:

[tex]\[ y = 29 \left( \frac{1}{2} \right)^{\frac{t}{45}} \][/tex]

In this problem, [tex]\( t = 150 \)[/tex] years. We need to substitute the values into the formula and perform the calculations step-by-step.

1. Identify the given values:

- Initial mass, [tex]\( y_0 = 29 \)[/tex] grams.
- Half-life, [tex]\( \text{half-life} = 45 \)[/tex] years.
- Time, [tex]\( t = 150 \)[/tex] years.

2. Substitute the values into the formula:

[tex]\[ y = 29 \left( \frac{1}{2} \right)^{\frac{150}{45}} \][/tex]

3. Simplify the exponent:

[tex]\[ \frac{150}{45} = \frac{150 \div 15}{45 \div 15} = \frac{10}{3} \][/tex]

So we rewrite the formula as:

[tex]\[ y = 29 \left( \frac{1}{2} \right)^{\frac{10}{3}} \][/tex]

4. Calculate the exponentiation:

[tex]\[ \left( \frac{1}{2} \right)^{\frac{10}{3}} \approx 0.099212565748012 \][/tex]

5. Multiply by the initial mass:

[tex]\[ y = 29 \times 0.099212565748012 \approx 2.877164406692361 \][/tex]

So, the remaining mass of the radioactive element after 150 years is approximately [tex]\( 2.877164406692361 \)[/tex] grams.

6. Round the result to three decimal places:

[tex]\[ y \approx 2.877 \][/tex]

Therefore, the remaining mass after 150 years is approximately [tex]\( 2.877 \)[/tex] grams.