To solve this we are going to use the future value of annuity due formula:
![FV=(1+ \frac{r}{n} )*P[ \frac{(1+ \frac{r}{n})^{kt}-1 }{ \frac{r}{n} } ]](https://tex.z-dn.net/?f=FV%3D%281%2B%20%5Cfrac%7Br%7D%7Bn%7D%20%29%2AP%5B%20%5Cfrac%7B%281%2B%20%5Cfrac%7Br%7D%7Bn%7D%29%5E%7Bkt%7D-1%20%7D%7B%20%5Cfrac%7Br%7D%7Bn%7D%20%7D%20%5D)
where
is the future value
is the periodic deposit
is the interest rate in decimal form
is the number of times the interest is compounded per year
is the number of deposits per year
We know for our problem that
and
. To convert the interest rate to decimal form, we are going to divide the rate by 100%:
. Since Ruben makes the deposits every 6 months,
. The interest is compounded semiannually, so 2 times per year; therefore,
.
Lets replace the values in our formula:
![FV=(1+ \frac{0.1}{2} )*420[ \frac{(1+ \frac{0.1}{2})^{(2)(15)}-1 }{ \frac{01}{2} } ]](https://tex.z-dn.net/?f=FV%3D%281%2B%20%5Cfrac%7B0.1%7D%7B2%7D%20%29%2A420%5B%20%5Cfrac%7B%281%2B%20%5Cfrac%7B0.1%7D%7B2%7D%29%5E%7B%282%29%2815%29%7D-1%20%7D%7B%20%5Cfrac%7B01%7D%7B2%7D%20%7D%20%5D)
We can conclude that the correct answer is <span>
$29,299.53</span>
*I am assuming that the hexagons in all questions are regular and the triangle in (24) is equilateral*
(21)
Area of a Regular Hexagon: 
square units
(22)
Similar to (21)
Area = 
square units
(23)
For this case, we will have to consider the relation between the side and inradius of the hexagon. Since, a hexagon is basically a combination of six equilateral triangles, the inradius of the hexagon is basically the altitude of one of the six equilateral triangles. The relation between altitude of an equilateral triangle and its side is given by:
Hence, area of the hexagon will be: 
square units
(24)
Given is the inradius of an equilateral triangle.
Substituting the value of inradius and calculating the length of the side of the equilateral triangle:
Side = 16 units
Area of equilateral triangle = 
square units
For this case, the first thing we must do is define a variable.
We have then:
x: unknown number
We now write the equation that models the problem:
From here, we clear the value of x.
We multiply both sides of the equation by 2:
We subtract 30 on both sides of the equation:
Answer:
The value of the unknown number is given by:
The 3 inside angles of a triangle equal 180.
Add the 3 angles together to equal 180:
X + (5x-20) + 4x = 180
Simplify the left side by adding like terms:
10x-20 = 180
Add 20 to each side:
10x = 200
Divide both sides by 10:
x = 20
Angle A = x = 20
Angle B = 4X = 4(20) = 80
Angle C = 5x-20 = 5(20) -20 = 100-20 = 80
