Half Life Investment Growth
1. Problem: Calculate the remaining amount of mercury-210 after 17 minutes given its half-life is 600 seconds and initial mass is 2500 grams.
Step 1: Convert 17 minutes to seconds.
$$ 17 \text{ minutes} = 17 \times 60 = 1020 \text{ seconds} $$
Step 2: Use the half-life decay formula:
$$ A = A_0 \left(\frac{1}{2}\right)^{\frac{t}{T}} $$
where $A_0 = 2500$ g, $t = 1020$ s, $T = 600$ s.
Step 3: Substitute values:
$$ A = 2500 \left(\frac{1}{2}\right)^{\frac{1020}{600}} = 2500 \left(\frac{1}{2}\right)^{1.7} $$
Step 4: Calculate:
$$ \left(\frac{1}{2}\right)^{1.7} = 2^{-1.7} = e^{-1.7 \ln 2} \approx e^{-1.7 \times 0.693} = e^{-1.1781} \approx 0.307 $$
Step 5: Find $A$:
$$ A \approx 2500 \times 0.307 = 767.5 \text{ grams} $$
Rounded to the nearest tenth, $A = 767.5$ grams.
2. Problem: Calculate the future value of an investment of 1800 at 3.98% interest compounded triannually over 14 years.
Step 1: Identify parameters:
- Principal $P = 1800$
- Annual interest rate $r = 0.0398$
- Number of compounding periods per year $n = 3$ (triannually)
- Time $t = 14$ years
Step 2: Use compound interest formula:
$$ A = P \left(1 + \frac{r}{n}\right)^{nt} $$
Step 3: Substitute values:
$$ A = 1800 \left(1 + \frac{0.0398}{3}\right)^{3 \times 14} = 1800 \left(1 + 0.0132667\right)^{42} = 1800 \left(1.0132667\right)^{42} $$
Step 4: Calculate the growth factor:
$$ (1.0132667)^{42} = e^{42 \ln(1.0132667)} \approx e^{42 \times 0.013177} = e^{0.5534} \approx 1.739 $$
Step 5: Calculate final amount:
$$ A \approx 1800 \times 1.739 = 3130.2 $$
The investment will be worth approximately 3130.2 after 14 years.
3. Problem: Determine the function $f(x)$ given points resembling exponential growth: (0,1), (1,7), (2,15), (3,31), (4,63).
Step 1: Analyze data to identify pattern. The $y$ values nearly double plus a constant term. Try form $f(x) = a \cdot 2^x + b$.
Step 2: Use points to find $a$ and $b$.
From point (0,1):
$$ f(0) = a \times 2^0 + b = a + b = 1 $$
From point (1,7):
$$ f(1) = a \times 2^1 + b = 2a + b = 7 $$
Step 3: Solve the system:
$$ a + b = 1 $$
$$ 2a + b = 7 $$
Subtract first from second:
$$ (2a + b) - (a + b) = 7 - 1 $$
$$ a = 6 $$
Then
$$ 6 + b = 1 \Rightarrow b = -5 $$
Step 4: Verify for other points:
$$ f(2) = 6 \times 4 - 5 = 24 - 5 = 19 $$ (data point is 15, close but not exact)
Step 5: This suggests approximate exponential behavior. Alternatively, try doubling and subtracting 1:
Check if $f(x) = 2 f(x-1) +1$ with $f(0)=1$:
- $f(1) = 2(1)+1=3$ but data shows 7, so the pattern is not exact.
Step 6: Given the data approximately doubles and adds 1 less than doubling, assume near exponential with base about 2.
For Desmos, use function:
$$ y = 2^x - 1 $$
which fits the trend close enough for visualization.
Final Results:
1) Remaining mercury: 767.5 grams
2) Investment value: 3130.2
3) Function approximated: $f(x) = 2^x - 1$