The elevation of city A is 96 feet below sea level; the elevation of city C is 24 feet below sea level. The elevation of city D
1 answer:
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Answer:
- P(t) = 100·2.3^t
- 529 after 2 hours
- 441 per hour, rate of growth at 2 hours
- 5.5 hours to reach 10,000
Step-by-step explanation:
It often works well to write an exponential expression as ...
value = (initial value)×(growth factor)^(t/(growth period))
(a) Here, the growth factor for the bacteria is given as 230/100 = 2.3 in a period of 1 hour. The initial number is 100, so we can write the pupulation function as ...
P(t) = 100·2.3^t
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(b) P(2) = 100·2.3^2 = 529 . . . number after 2 hours
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(c) P'(t) = ln(2.3)P(t) ≈ 83.2909·2.3^t
P'(2) = 83.2909·2.3^2 ≈ 441 . . . bacteria per hour
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(d) We want to find t such that ...
P(t) = 10000
100·2.3^t = 10000 . . . substitute for P(t)
2.3^t = 100 . . . . . . . . divide by 100
t·log(2.3) = log(100)
t = 2/log(2.3) ≈ 5.5 . . . hours until the population reaches 10,000
Answer:
According to the rule of 72, the doubling time for this interest rate is 8 years.
The exact doubling time of this amount is 8.04 years.
Step-by-step explanation:
Sometimes, the compound interest formula is quite complex to be solved, so the result can be estimated by the rule of 72.
By the rule of 72, we have that the doubling time D is given by:
The interest rate is in %.
In our exercise, the interest rate is 9%. So, by the rule of 72:
.
According to the rule of 72, the doubling time for this interest rate is 8 years.
Exact answer:
The exact answer is going to be found using the compound interest formula.
In which A is the amount of money, P is the principal(the initial sum of money), r is the interest rate(as a decimal value), n is the number of times that interest is compounded per unit t and t is the time the money is invested or borrowed for.
So, for this exercise, we have:
We want to find the doubling time, that is, the time in which the amount is double the initial amount, double the principal.
is double the initial amount, double the principal.
The interest is compounded anually, so
Now, we apply the following log propriety:
So:
The exact doubling time of this amount is 8.04 years.