Algebra - GRE Quantitative Reasoning

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Question

For how many integers, , between 26 and 36 is it true that

$\frac{3}{x}_{,}\frac{4}{x}_{,}$ and $\frac{5}{x}$ are all in lowest terms?

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Answer

If is even, then $\frac{4}{x}$ is not in lowest terms, since both and 4 are divisible by 2. Therefore, the only possibilities are 27,29,31,33, and 35. But $\frac{3}{27}= \frac{1}{9}$ , $\frac{3}{33}= \frac{1}{11}$ , and $\frac{5}{35}= \frac{1}{7}$ , so only two integers satisfy the given condition: 29 and 31.

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Question

Mrs. Lawrence's class has students, of which are girls. If you were to choose a student at random, what's the probability that the student chosen would be a boy?

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Answer

In order to find out the probability of choosing a boy, you must first find out how many boys there are. Since there are girls out of students, students should be boys.

Therefore, the probability of choosing a boy is,

$\frac{21}{35}$ .

However, this is not one of the answer choices; therefore, you must reduce the fraction.

In order to reduce a fraction, you have to find their GCM, or greatest common multiple. This is the biggest number that will go into both the numerator and denominator . The largest number is . Divide both the top and bottom by , and you will get the answer:

$\frac{3}{5}$

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Question

Simplify the fraction:

$\frac{0.0003(0.4)(0.0002)}{0.00000006(0.01)}$

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Answer

To simplify the fraction

$\frac{0.0003(0.4)(0.0002)}{0.00000006(0.01)}$

It may be helpful to write it in terms of scientific notation:

$\frac{3\cdot 10^{-4}(4\cdot 10^{-1})(2\cdot 10^{-4})}{6\cdot 10^{-8}(1\cdot 10^{-2})}$

$\frac{24\cdot 10^{-4-1-4}}{6\cdot 10^{-8-2}}$

$\frac{24\cdot 10^{-9}}{6\cdot 10^{-10}}$

$4\cdot10^{-9+10}$

$4\cdot10$

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Question

Simply the fraction:

$\frac{4a^3+12a^2b+12ab^2+4b^3}{3a^2+6ab+3b^2}$

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Answer

To simplify the fraction

$\frac{4a^3+12a^2b+12ab^2+4b^3}{3a^2+6ab+3b^2}$

Begin by factoring out common terms in the numerator and denominator:

$\frac{4(a^3+3a^2b+3ab^2+b^3)}{3(a^2+2ab+b^2)}$

Now notice that the coefficients for the polynomials in the numerator and denominator match the form of Pascal's Triangle:

The fraction can be rewritten as:

$\frac{4(a+b)^3}{3(a+b)^2}$

And finally reduced to

$\frac{4}{3}(a+b)$

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Question

Simplify: y3x4(yx3 + y2x2 + y15 + x22)

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Answer

When you multiply exponents, you add the common bases:

y4 x7 + y5x6 + y18x4 + y3x26

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Question

Indicate whether Quantity A or Quantity B is greater, or if they are equal, or if there is not enough information given to determine the relationship.

$\dpi{100} \small n>0$

Quantity A: $\dpi{100} \small 16^{n+2}$

Quantity B: $\dpi{100} \small 2^{4}\times (8^{n+1})^{2}\div 4^{n}$

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Answer

By using exponent rules, we can simplify Quantity B.

$\dpi{100} \small \dpi{100} \small 2^{4}\times (8^{n+1})^{2}\div 4^{n}$

$\dpi{100} \small \dpi{100} \small 2^{4}\times (8^{2n+2})\div 4^{n}$

$\dpi{100} \small \dpi{100} \small 2^{4}\times 2^{3(2n+2)}\div 4^{n}$

$\dpi{100} \small \dpi{100} \small 2^{4}\times 2^{6n+6}\div 4^{n}$

$\dpi{100} \small \dpi{100} \small 2^{6n+10}\div 4^{n}$

$\dpi{100} \small \dpi{100} \small 2^{6n+10}\div 2^{2n}$

$\dpi{100} \small 2^{4n+10}$

Also, we can simplify Quantity A.

$\dpi{100} \small 16^{n+2}$

$\dpi{100} \small =2^{4(n+2)}$

$\dpi{100} \small =2^{4n+8}$

Since n is positive, $\dpi{100} \small 4n+10>4n+8$

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Question

If $5^2 \times 5^n = 5^{12}$ , what is the value of ?

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Answer

Since the base is 5 for each term, we can say 2 + n =12. Solve the equation for n by subtracting 2 from both sides to get n = 10.

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Question

If $\frac{3^{y - 1}}{3^{-2}} = 27^{y}3^{y}$ , what is the value of ?

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Answer

Rewrite the term on the left as a product. Remember that negative exponents shift their position in a fraction (denominator to numerator).

$3^{y-1}3^2=27^y3^y$

The term on the right can be rewritten, as 27 is equal to 3 to the third power.

$3^{y-1}3^2=(3^3)^y3^y$

Exponent rules dictate that multiplying terms allows us to add their exponents, while one term raised to another allows us to multiply exponents.

$3^{(y-1)+2}=(3)^{3y}3^y$

$3^{y+1}=3^{3y+y}=3^{4y}$

We now know that the exponents must be equal, and can solve for .

$\frac{1}{3}=y$

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Question

Simplify $x^{^{3}}x^{^{5}} - x^{^{2}} + (y^{^{2}})^{^{2}}$ .

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Answer

First, simplify $x^{3}x^{5}$ by adding the exponents to get $x^{8}$ .

Then simplify $(y^{2})^{2}$ by multiplying the exponents to get $y^{4}$ .

This gives us $x^{8} - x^{^{2}} + y^{4}$ . We cannot simplify any further.

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Question

Simplify $x^{3}x^{6} + (x^{3})^{3} + x^{3}x^{2}x^{2}x^{2}$ .

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Answer

Start by simplifying each individual term between the plus signs. We can add the exponents in and so each of those terms becomes . Then multiply the exponents in so that term also becomes . Thus, we have simplified the expression to which is $3x^{9}$ .

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Question

If $3^4 \cdot 3^8 = 9^x$ , what is the value of

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Answer

To attempt this problem, note that .

Now note that when multiplying numbers, if the base is the same, we may add the exponents:

$3^4 \cdot 3^8 = 3^{4+8}=3^{12}$

This can in turn be written in terms of nine as follows (recall above)

$3^{12}=9^{\frac{12}{2}}=9^6$

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Question

If $(3^2\cdot3^5)^3=3^x$ , what is the value of

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Answer

When dealing with exponenents, when multiplying two like bases together, add their exponents:

$3^2\cdot3^5=3^7$

However, when an exponent appears outside of a parenthesis, or if the entire number itself is being raised by a power, multiply:

$(3^7)^3=3^{7\cdot 3}=3^{21}$

$3^{21}=3^{x}$

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Question

If $c\neq 0$ , then $\frac{(c^3)^2}{c^2c^4}=?$

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Answer

Start by simplifying the numerator and denominator separately. In the numerator, (c3)2 is equal to c6. In the denominator, c2 * c4 equals c6 as well. Dividing the numerator by the denominator, c6/c6, gives an answer of 1, because the numerator and the denominator are the equivalent.

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Question

Evaluate:

$\frac{(2x^3y^{-2}a^6z^4)^5}{(4xy^4a^{-3}z^4)^2}$

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Answer

Distribute the outside exponents first:

$\frac{2^5x^{15}y^{-10}a^{30}z^{20}}{4^2x^2y^8a^{-6}z^8}$

Divide the coefficient by subtracting the denominator exponents from the corresponding numerator exponents:

$\frac{2x^{13}a^{36}z^{12}}{y^{18}}$

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Question

If $a\not\equiv0$ , which of the following is equal to $\frac{(a^6*a^2)^3}{a^6}$ ?

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Answer

The numerator is simplified to (by adding the exponents), then cube the result. a24/a6 can then be simplified to $a^{18}$ .

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Question

\[641/2 + (–8)1/3\] * \[43/16 – 3171/3169\] =

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Answer

Let's look at the two parts of the multiplication separately. Remember that (–8)1/3 will be negative. Then 641/2 + (–8)1/3 = 8 – 2 = 6.

For the second part, we can cancel some exponents to make this much easier. 43/16 = 43/42 = 4. Similarly, 3171/3169 = 3171–169 = 32 = 9. So 43/16 – 3171/3169 = 4 – 9 = –5.

Together, \[641/2 + (–8)1/3\] * \[43/16 – 3171/3169\] = 6 * (–5) = –30.

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Question

$\dpi{100} \small \frac{7^{10}-7^{8}}{7^{9}-7^{7}}=$

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Answer

The easiest way to solve this is to simplify the fraction as much as possible. We can do this by factoring out the greatest common factor of the numerator and the denominator. In this case, the GCF is .

$\frac{7^7\left ( 7^3-7^1\right)}{7^7\left ( 7^2-1\right)}$

Now, we can cancel out the from the numerator and denominator and continue simplifying the expression.

$\frac{7^7\left ( 7^3-7^1\right)}{7^7\left ( 7^2-1\right)}=\frac{7^3-7^1}{7^2-1}=\frac{343-7}{49-1}=\frac{336}{48}=7$

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Question

(b * b4 * b7)1/2/(b3 * bx) = b5

If b is not negative then x = ?

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Answer

Simplifying the equation gives b6/(b3+x) = b5.

In order to satisfy this case, x must be equal to –2.

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Question

If〖7/8〗n= √(〖7/8〗5),then what is the value of n?

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Answer

7/8 is being raised to the 5th power and to the 1/2 power at the same time. We multiply these to find n.

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Question

is a real number such that $y\geq 1$ .

Quantity A:

Quantity B:

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Answer

(y2)(y4) = y2+4 = y6

Plug in two different values for y.

Plug in y = 1: y8 = y6

Plug in y = 2: y8 > y6

Since the results differ, the relationship cannot be determined from the information given.

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