decimal notation

Expert replies

hakyology: Senior | Next Rank: 100 Posts; Posts: 66; Joined: Tue Jun 05, 2007 1:39 pm; Thanked: 1 times

by hakyology » Mon Jul 07, 2008 7:06 am

What is the least number of digits (including repetitions) needed to express 10^100 in decimal notation?
A)4
B)100
C)101
D)1,000
E)1,001

Please explain.

The answer is C.

Thank you.

Like this post

Source: Beat The GMAT — Problem Solving | Mon Jul 07, 2008 7:06 am

sethids: Master | Next Rank: 500 Posts; Posts: 135; Joined: Mon Jun 23, 2008 3:56 am; Thanked: 7 times

by sethids » Mon Jul 07, 2008 7:32 am

10^100 means writing 1 followed by 100 zeroes.
Hence 101 digits are required to represent it in decimal notation.

Like this post

dalwow: Senior | Next Rank: 100 Posts; Posts: 36; Joined: Tue Oct 02, 2007 10:25 am; Thanked: 2 times

by dalwow » Wed Jul 09, 2008 11:04 am

Another way to think about it is this....imagine you have 100 10's lined up to multiply by each other. Multiply the first 2 and you get 100 which is 3 digits. Now you know that each additional 10 will add one more digit. You have 98 more 10's, so you take the 3 digits you already have and add the 98 additional digits and you get 101.

Still Learning

Like this post

lightbulb: Senior | Next Rank: 100 Posts; Posts: 34; Joined: Wed Jul 09, 2008 6:40 pm; Thanked: 3 times

by lightbulb » Wed Jul 09, 2008 9:10 pm

10^1 = 10 Use 2 digits (1 + 1)
10^2 = 100 Use 3 digits (2 + 1)
10^3 = 1000 Use 4 digits (3 + 1)

=> 10^n would require n+1 digits

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review