What is the volume of a cone with a base radius of 5 m and a height of 12 m
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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.
Given:
Number of students = 35
Two out of every five boys in the club are boys.
To find:
The number of students in the club that are boys.
Solution:
Two out of every five boys in the club are boys. It means, the ratio of boys to the total number of student is 2:5.
Let the number of boys be 2x and number of students be 5x.
According to the question,
Now, the number of boys is
Therefore, 14 students in the club are boys.