Which of the following is closest in value to (9^9)-(9^2)?

Question

A. 9^9
B. 9^8
C. 9^7
D. 9^6
E. 9^5

Bunuel · Accepted Answer

Easier way:  9^9 - 9^2=9^2(9^7-1) . Now  9^7-1  is very close to  9^7 , hence  9^9 - 9^2=9^2(9^7-1)\approx{9^2*9^7=9^9} .

Answer: A.

pmenon · Answer

i would say A as well ... i just simplified out to 9^2*(9^7 - 1) ... and the 1 is pretty much negligible ... so we go back down to 9^9 ...

jallenmorris · Answer

I think the answer is going to be A. The reason is that subtracting 81 from 9^9 is not going to subtract enough to get it anywhere close to 9^8. 9^8 is going to be such a huge number that when you multiply it by 9 again to get 9^9, subtracting 81 (i.e., 9^2) from it, the result will still be must closer to 9^9 than any of the others.

puma

Which of the following is closest in value to (9^9)-(9^2)?

a) 9^9
b) 9^8
c) 9^7
d) 9^6
e) 9^5

shalva · Answer

We need to get approximate answer. I'm pretty sure exact number is unreachable w/o Excel spreadsheets.

bibha · Answer

Which of the following is closest to 9^9 - 9^2?

A. 9^9
B. 9^8
C. 9^7
D. 9^6
E. 9^5

gurpreetsingh · Answer

IMO A, whats the OA? clearly 9^8 <9^9 - 9^2 < 9^9 now 9^9 - 9^2 will be closer to 9^9 if 9^9 - 9^2? lies between \frac{(9^9+9^8)}{2} and 9^9 else 9^8 \frac{(9^9+9^8)}{2} = 9^8*\frac{(9+1)}{2} = 9^{8} * 5 9^9 - 9^2 = 9^8( 9 - 9^{-6}) > 9^8 * 8 > 9^8*5 since 9^9 - 9^2 is greater than \frac{(9^9+9^8)}{2} i.e 9^{8} * 5 This lies closer to 9^9

PareshGmat · Answer

Answer = A
9^9 is way too high compared to 9^2

Bunuel · Answer

9^9 is much larger number than 9^2 and as we need approximate value then it's pretty much negligible in this case, so: (9^9)-(9^2) = ~9^9. Answer: A. Similar questions to practice: the-value-of-10-8-10-2-10-7-10-3-is-closest-to-which-of-95082.html which-of-the-following-is-closest-to-10180-1030-a-110224.html which-of-the-following-best-approximates-the-value-of-q-if-99674.html new-tough-and-tricky-exponents-and-roots-questions-125956-40.html if-x-10-10-x-2-2x-7-3x-2-10x-2-is-closest-to-143897.html 1-0-0001-0-04-10-the-value-of-the-expression-above-is-59398.html m24-q-7-explanation-76513.html 10-180-10-30-which-of-the-following-best-approximates-84309.html if-x-2-b-8-8-8-6-for-which-of-the-following-b-values-160197.html if-x-3-000-then-the-value-of-x-2x-1-is-closest-to-166128.html Hope it helps.

PareshGmat · Answer

9^9  is way too high than  9^2

So answer = A = 9^9

bumpbot · Answer

Automated notice from GMAT Club BumpBot: 

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

 This post was generated automatically.

Which of the following is closest in value to (9^9)-(9^2)?

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Problem Solving (PS) Questions

Which of the following is closest in value to (9^9)-(9^2)?

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards