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.

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:

Yes D is correct answer. If you subtract 1 from 10^20 it will be 999(20 times) if you subtract 15 more from that, you will get last digit 4 second last 8 and all others 9. So answer is D.

Yes D is correct answer. If you subtract 1 from 10^20 it will be 999(20 times) if you subtract 15 more from that, you will get last digit 4 second last 8 and all others 9. So answer is D.

I did it the same way. Subtracting 1 first seemed to help me visualize it.

Well, 10^2-16=84 and 10^3-16 = 984. So, we see the exponent tells us the number of digits involved in our answer (2 in the former case, 3 in the latter).

10^2^0-16=999...984; two numbers are the 8 and the 4, whereas the other eighteen are 9s!

10^2^0 would be a 21 digit number ... subtract 16 and you are left with a 20 digit number with 2 digits as 4 and 8 and the rest 9s. The total is 8+4+18*9 = 174 therefore (D) _________________

What is the sum of the digits in decimal notation of number 10^{20}-16?

A. 158 B. 162 C. 165 D. 174 E. 183

10^{20} has 21 digits: 1 followed by 20 zeros; 10^{20}-16 has 20 digits: 18 9's and 84 in the end;

So, the sum of the digits of 10^{20}-16 equals to 18*9+8+4=174.

Answer: D.

D can't be the answer. once we subtract 16 from 10^20 we have only 19 numbers left. among 19 numbers 17 are nine and last two are 8 and 4. therefor sum is 17*9+8+4=165

What is the sum of the digits in decimal notation of number 10^{20}-16?

A. 158 B. 162 C. 165 D. 174 E. 183

10^{20} has 21 digits: 1 followed by 20 zeros; 10^{20}-16 has 20 digits: 18 9's and 84 in the end;

So, the sum of the digits of 10^{20}-16 equals to 18*9+8+4=174.

Answer: D.

D can't be the answer. once we subtract 16 from 10^20 we have only 19 numbers left. among 19 numbers 17 are nine and last two are 8 and 4. therefor sum is 17*9+8+4=165

Nope.

10^{20} has 21 digits: 1 followed by 20 zeros: 100,000,000,000,000,000,000

10^{20}-16 has 20 digits: 18 9's and 84 in the end: 99,999,999,999,999,999,984. _________________