Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Exponents and roots problems are very common on the GMAT. So, it's extremely important to know how to manipulate them, how to factor out, take roots, multiply, divide, etc. Below are 11 problems to test your skills. Please post your thought process/solutions along with the answers.

I'll post OA's with detailed solutions tomorrow. Good luck.

1. What is the value of \(\sqrt{25+10\sqrt{6}}+\sqrt{25-10\sqrt{6}}\)? A. \(2\sqrt{5}\) B. \(\sqrt{55}\) C. \(2\sqrt{15}\) D. 50 E. 60

5. If \(x=23^2*25^4*27^6*29^8\) and is a multiple of \(26^n\), where \(n\) is a non-negative integer, then what is the value of \(n^{26}-26^n\)? A. -26 B. -25 C. -1 D. 0 E. 1

7. If \(x=\sqrt{10}+\sqrt[3]{9}+\sqrt[4]{8}+\sqrt[5]{7}+\sqrt[6]{6}+\sqrt[7]{5}+\sqrt[8]{4}+\sqrt[9]{3}+\sqrt[10]{2}\), then which of the following must be true: A. x<6 B. 6<x<8 C. 8<x<10 D. 10<x<12 E. x>12

8. If \(x\) is a positive number and equals to \(\sqrt{6+{\sqrt{6+\sqrt{6+\sqrt{6+...}}}}}\), where the given expression extends to an infinite number of roots, then what is the value of x? A. \(\sqrt{6}\) B. 3 C. \(1+\sqrt{6}\) D. \(2\sqrt{3}\) E. 6

9. If \(x\) is a positive integer then the value of \(\frac{22^{22x}-22^{2x}}{11^{11x}-11^x}\) is closest to which of the following? A. \(2^{11x}\) B. \(11^{11x}\) C. \(22^{11x}\) D. \(2^{22x}*11^{11x}\) E. \(2^{22x}*11^{22x}\)

10. Given that \(5x=125-3y+z\) and \(\sqrt{5x}-5-\sqrt{z-3y}=0\), then what is the value of \(\sqrt{\frac{45(z-3y)}{x}}\)? A. 5 B. 10 C. 15 D. 20 E. Can not be determined

Re: NEW!!! Tough and tricky exponents and roots questions [#permalink]

Show Tags

12 Jan 2012, 12:36

1

This post received KUDOS

5. If x=23^2*25^4*27^6*29^8 and is a multiple of 26^n, where n is a non-negative integer, then what is the value of n^26-26^n? A. -26 B. -25 C. -1 D. 0 E. 1

Re: NEW!!! Tough and tricky exponents and roots questions [#permalink]

Show Tags

12 Jan 2012, 12:51

1

This post received KUDOS

8. If x is a positive number and equals to \sqrt{6+{\sqrt{6+\sqrt{6+\sqrt{6+...}}}}}, where the given expression extends to an infinite number of roots, then what is the value of x? A. \sqrt{6} B. 3 C. 1+\sqrt{6} D. 2\sqrt{3} E. 6

x= √(6+√(6+√(6+... x^2 = 6 + x x^2-x-6=0 (x-3)(x+2) = 0 x = 3 or -2 Value of sqrt cant be -ve Option

Re: NEW!!! Tough and tricky exponents and roots questions [#permalink]

Show Tags

12 Jan 2012, 13:01

10. Given that 5x=125-3y+z and \sqrt{5x}-25-\sqrt{z-3y}=0, then what is the value of \sqrt{\frac{45(z-3y)}{x}}? A. 5 B. 10 C. 15 D. 20 E. Can not be determined

5x-125=z-3y

sqrt{5x}-25=\sqrt{z-3y} (sqrt{5x}-25)^2=z-3y

(sqrt{5x}-25)^2=5x-125 \sqrt{5x}=15 x=5*9=45

so the expression \sqrt{\frac{45(z-3y)}{x} = \sqrt{45(15-25)/45}=\sqrt{-10}

E is the answ
_________________

Happy are those who dream dreams and are ready to pay the price to make them come true

I am still on all gmat forums. msg me if you want to ask me smth

Re: NEW!!! Tough and tricky exponents and roots questions [#permalink]

Show Tags

12 Jan 2012, 13:07

7. If x=\sqrt{10}+\sqrt[3]{9}+\sqrt[4]{8}+\sqrt[5]{7}+\sqrt[6]{6}+\sqrt[7]{5}+\sqrt[8]{4}+\sqrt[9]{3}+\sqrt[10]{2}, then which of the following must be true: A. x<6 B. 6<x<8 C. 8<x<10 D. 10<x<12 E. x>12

my answ to this q is intuitive.

everyone knows that sqroot10=3.16 \sqrt[3]{9} is approx \sqrt[3]{2^3} >2 (but less than 3) the rest of roots are more than 1 and less than 2

so we have 3.16+2,..+1+1+1+1+1+1+1 = approx 12.16

E is the answ
_________________

Happy are those who dream dreams and are ready to pay the price to make them come true

I am still on all gmat forums. msg me if you want to ask me smth

Re: NEW!!! Tough and tricky exponents and roots questions [#permalink]

Show Tags

12 Jan 2012, 13:17

9. If x is a positive integer then the value of \frac{22^{22x}-22^{2x}}{11^{11x}-11^x} is closest to which of the following? A. 2^{11x} B. 11^{11x} C. 22^{11x} D. 2^{22x}*11^{11x} E. 2^{22x}*11^{22x}

3. If \(5^{10x}=4,900\) and \(2^{\sqrt{y}}=25\) what is the value of \(\frac{5^{(x-1)^5}}{4^{-\sqrt{y}}\)? A. 14/5 B. 5 C. 28/5 D. 13 E. 14

5. If \(x=23^2*25^4*27^6*29^8\) and is a multiple of \(26^n\), where \(n\) is a non-negative integer, then what is the value of \(n^26-26^n\)? A. -26 B. -25 C. -1 D. 0 E. 1

Welcome back Bunuel!

Some nice questions. A couple of comments:

Q5 has a typo at the end: \(n^26-26^n\). I think you need to include the exponent 26 in braces {26} to get \(n^{26}-26^n\)

In Q3, unless I'm making some kind of stupid mistake, the value of the expression in the question is close to 600 (so isn't among the answers). I'm wondering if you meant the question to instead read something more like:

3. If \(5^{10x}=4,900\) and \(4^{\sqrt{y}}=25\) what is the value of \(\frac{5^{5x-1}}{2^{\sqrt{y}}\)? A. 14/5 B. 5 C. 28/5 D. 13 E. 14

In that case, I get one of the five answer choices (A).
_________________

GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

9. If x is a positive integer then the value of \frac{22^{22x}-22^{2x}}{11^{11x}-11^x} is closest to which of the following? A. 2^{11x} B. 11^{11x} C. 22^{11x} D. 2^{22x}*11^{11x} E. 2^{22x}*11^{22x}

And it looks as though every other question has been solved except for this one. I won't solve it completely, but I'll help people get started. Here, since we are asked for an approximation only, we don't need to compute an exact value. You might notice that if x is a positive integer, \(22^{22x}\) is vastly bigger than \(22^{2x}\). Since that's true, if we only need to estimate, we can ignore the small term. We can do the same thing in the denominator.
_________________

GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

Re: NEW!!! Tough and tricky exponents and roots questions [#permalink]

Show Tags

12 Jan 2012, 13:48

IanStewart wrote:

And it looks as though every other question has been solved except for this one. I won't solve it completely, but I'll help people get started. Here, since we are asked for an approximation only, we don't need to compute an exact value. You might notice that if x is a positive integer, \(22^{22x}\) is vastly bigger than \(22^{2x}\). Since that's true, if we only need to estimate, we can ignore the small term. We can do the same thing in the denominator.

And it looks as though every other question has been solved except for this one. I won't solve it completely, but I'll help people get started. Here, since we are asked for an approximation only, we don't need to compute an exact value. You might notice that if x is a positive integer, \(22^{22x}\) is vastly bigger than \(22^{2x}\). Since that's true, if we only need to estimate, we can ignore the small term. We can do the same thing in the denominator.

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

3. If \(5^{10x}=4,900\) and \(2^{\sqrt{y}}=25\) what is the value of \(\frac{5^{(x-1)^5}}{4^{-\sqrt{y}}\)? A. 14/5 B. 5 C. 28/5 D. 13 E. 14

5. If \(x=23^2*25^4*27^6*29^8\) and is a multiple of \(26^n\), where \(n\) is a non-negative integer, then what is the value of \(n^26-26^n\)? A. -26 B. -25 C. -1 D. 0 E. 1

Welcome back Bunuel!

Some nice questions. A couple of comments:

Q5 has a typo at the end: \(n^26-26^n\). I think you need to include the exponent 26 in braces {26} to get \(n^{26}-26^n\)

In Q3, unless I'm making some kind of stupid mistake, the value of the expression in the question is close to 600 (so isn't among the answers). I'm wondering if you meant the question to instead read something more like:

3. If \(5^{10x}=4,900\) and \(4^{\sqrt{y}}=25\) what is the value of \(\frac{5^{5x-1}}{2^{\sqrt{y}}\)? A. 14/5 B. 5 C. 28/5 D. 13 E. 14

In that case, I get one of the five answer choices (A).

Hello Ian. Glad to be back!

Thanks for your comments. Yes, there were 2 typos: For Q5: included the exponent 26 in braces {26} to avoid confusion; For Q3: added the brackets which were lost in copy/past, it should read \(\frac{(5^{(x-1)})^5}{4^{-\sqrt{y}}\).
_________________

Re: NEW!!! Tough and tricky exponents and roots questions [#permalink]

Show Tags

13 Jan 2012, 14:39

LalaB wrote:

2. What is the units digit of (17^3)^4-1973^{3^2}? A. 0 B. 2 C. 4 D. 6 E. 8

7^12-3^9 11-3=8

ANS IS E

Bunuel wrote:

2. What is the units digit of \((17^3)^4-1973^{3^2}\)? A. 0 B. 2 C. 4 D. 6 E. 8

i believe the answer is : 7^12-3^6 ---> 11-9= 2 ---> B

note: I believe the part I wrote (which i colored red) is wrong. Can someone explain why? when an exponent is raised to another exponent then what operation should we do first? - Okey! Just read the rules about routs that Bunuel posted and found my mistake! (exponentiation by stacked symbols)

Last edited by SonyGmat on 14 Jan 2012, 00:11, edited 6 times in total.

Re: NEW!!! Tough and tricky exponents and roots questions [#permalink]

Show Tags

13 Jan 2012, 16:09

LalaB wrote:

10. Given that 5x=125-3y+z and \sqrt{5x}-25-\sqrt{z-3y}=0, then what is the value of \sqrt{\frac{45(z-3y)}{x}}? A. 5 B. 10 C. 15 D. 20 E. Can not be determined

5x-125=z-3y

sqrt{5x}-25=\sqrt{z-3y} (sqrt{5x}-25)^2=z-3y

(sqrt{5x}-25)^2=5x-125 \sqrt{5x}=15 x=5*9=45

so the expression \sqrt{\frac{45(z-3y)}{x} = \sqrt{45(15-25)/45}=\sqrt{-10}

E is the answ

bunuel wrote:

10. Given that \(5x=125-3y+z\) and \(\sqrt{5x}-25-\sqrt{z-3y}=0\), then what is the value of \(\sqrt{\frac{45(z-3y)}{x}}\)? A. 5 B. 10 C. 15 D. 20 E. Can not be determined

Re: NEW!!! Tough and tricky exponents and roots questions [#permalink]

Show Tags

13 Jan 2012, 19:42

1

This post received KUDOS

1

This post was BOOKMARKED

IanStewart wrote:

Bunuel wrote:

3. If \(5^{10x}=4,900\) and \(2^{\sqrt{y}}=25\) what is the value of \(\frac{5^{(x-1)^5}}{4^{-\sqrt{y}}\)? A. 14/5 B. 5 C. 28/5 D. 13 E. 14

5. If \(x=23^2*25^4*27^6*29^8\) and is a multiple of \(26^n\), where \(n\) is a non-negative integer, then what is the value of \(n^26-26^n\)? A. -26 B. -25 C. -1 D. 0 E. 1

Welcome back Bunuel!

Some nice questions. A couple of comments:

Q5 has a typo at the end: \(n^26-26^n\). I think you need to include the exponent 26 in braces {26} to get \(n^{26}-26^n\)

In Q3, unless I'm making some kind of stupid mistake, the value of the expression in the question is close to 600 (so isn't among the answers). I'm wondering if you meant the question to instead read something more like:

3. If \(5^{10x}=4,900\) and \(4^{\sqrt{y}}=25\) what is the value of \(\frac{5^{5x-1}}{2^{\sqrt{y}}\)? A. 14/5 B. 5 C. 28/5 D. 13 E. 14

In that case, I get one of the five answer choices (A).

then \(\sqrt{25+10\sqrt{6}}*\sqrt{25-10\sqrt{6}}=y\) So \(({25+10\sqrt{6}})*({25-10\sqrt{6}})=y^2\) so \(625-600=y^2\) so \(y=5\) so \(2ab=2y=10\) so \(x^2=a^2+b^2+2ab=50+10=60\) so \(x^2=60\) so \(x=\sqrt{4*15}\) so \(x=2\sqrt{15}\)

Hence Answer is C. \(2\sqrt{15}\)
_________________

"Nowadays, people know the price of everything, and the value of nothing."Oscar Wilde