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Example Questions
Example Question #13 : Gre Quantitative Reasoning
A five-year bond is opened with  in it and an interest rate ofÂ
%, compounded annually. This account is allowed to compound for five years. Which of the following most closely approximates the total amount in the account after that period of time?
Each year, you can calculate your interest by multiplying the principle () byÂ
. For one year, this would be:
For two years, it would be:
, which is the same asÂ
Therefore, you can solve for a five year period by doing:
Using your calculator, you can expand the  into a series of multiplications. This gives youÂ
, which is closest toÂ
.Â
Example Question #2 : How To Find Compound Interest
If a cash deposit account is opened with  for a three year period atÂ
% interest compounded once annually, which of the following is closest to the positive difference between the interest accrued in the third year and the interest accrued in the second year?
It is easiest to break this down into steps. For each year, you will multiply by  to calculate the new value. Therefore, let's make a chart:
After year 1:Â ; Total interest:Â
After year 2:Â ; Let us round this toÂ
; Total interest:Â
After year 3:Â ; Let us round this toÂ
; Total interest:Â
Thus, the positive difference of the interest from the last period and the interest from the first period is:Â
Example Question #1 : How To Find Compound Interest
Jack has ,
 to invest. If he invests two-thirds of it into a high-yield savings account with an annual interest rate of
, compounded quarterly, and the other third in a regular savings account at
 simple interest, how much does Jack earn after one year?
First, break the problem into two segments: the amount Jack invests in the high-yield savings, and the amount Jack invests in the simple interest account (10,000 and 5,000 respectively).
Now let's work with the high-yield savings account. $10,000 is invested at an annual rate of 8%, compounded quarterly. We can use the compound interest formula to solve:
Plug in the values given:
Therefore, Jack makes $824.32 off his high-yield savings account. Now let's calculate the other interest:
Â
Add the two together, and we see that Jack makes a total of,  off of his investments.
Example Question #1 : How To Find Compound Interest
A truck was bought for  in 2008, and it depreciates at a rate ofÂ
 per year. What is the value of the truck in 2016? Round to the nearest cent.
The first step is to convert the depreciation rate into a decimal. . Now lets recall the exponential decay model.Â
, whereÂ
 is the starting amount of money,Â
 is the annual rate of decay, andÂ
 is time (in years). After substituting, we get
Â
Â
Example Question #1 : How To Find Patterns In Exponents
If ax·a4 = a12 and (by)3 = b15, what is the value of x - y?
-2
-4
-9
6
3
3
Multiplying like bases means add the exponents, so x+4 = 12, or x = 8.
Raising a power to a power means multiply the exponents, so 3y = 15, or y = 5.
x - y = 8 - 5 = 3.
Example Question #1 : How To Find Patterns In Exponents
If p and q are positive integrers and 27p = 9q, then what is the value of q in terms of p?
3p
(3/2)p
(2/3)p
2p
p
(3/2)p
The first step is to express both sides of the equation with equal bases, in this case 3. The equation becomes 33p = 32q. So then 3p = 2q, and q = (3/2)p is our answer.Â
Example Question #3 : How To Find Patterns In Exponents
Simplify 272/3.
9
3
729
125
27
9
272/3 is 27 squared and cube-rooted. We want to pick the easier operation first. Here that is the cube root. To see that, try both operations.Â
272/3 = (272)1/3 = 7291/3 OR
272/3 = (271/3)2 = 32
Obviously 32 is much easier. Either 32 or 7291/3 will give us the correct answer of 9, but with 32 it is readily apparent.Â
Example Question #2 : Pattern Behaviors In Exponents
If  and
 are integers andÂ
Â
what is the value of ?Â
To solve this problem, we will have to take the log of both sides to bring down our exponents. By doing this, we will get .
To solve for  we will have to divide both sides of our equation by
 to getÂ
.
 will give you the answer of –3.
Example Question #3 : Pattern Behaviors In Exponents
If and
, then what is
?
We use two properties of logarithms:Â
So
Example Question #4 : Pattern Behaviors In Exponents
Evaluate:
, hereÂ
and
, hence
.
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