It is currently 25 Mar 2019, 23:58

### GMAT Club Daily Prep

#### 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

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

# How many 10-digit numbers can be formed using only the digit

Author Message
TAGS:
GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4857
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 105

Kudos [?]: 1783 [0], given: 397

How many 10-digit numbers can be formed using only the digit [#permalink]  30 Jul 2018, 10:49
Expert's post
00:00

Question Stats:

75% (00:38) correct 25% (00:26) wrong based on 12 sessions
How many 10-digit numbers can be formed using only the digits 2 and 5?

(A) $$2^{10}$$
(B) $$(22)(5!)$$
(C) $$(5!)(5!)$$
(D) $$\frac{10!}{2!}$$
(E) $$10!$$
[Reveal] Spoiler: OA

_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4857
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 105

Kudos [?]: 1783 [0], given: 397

Re: How many 10-digit numbers can be formed using only the digit [#permalink]  07 Aug 2018, 16:49
Expert's post
Explanation

This problem relies on the fundamental counting principle, which says that the total number of ways for something to happen is the product of the number of options for each individual choice.

For any digit of the 10-digit number there are exactly two options, a 2 or a 5. Thus, since there are two choices for each digit and it is a 10-digit number, there are $$(2)(2)(2)(2)(2)(2)(2)(2)(2)(2) = 2^{10}$$ total choices.
_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

Re: How many 10-digit numbers can be formed using only the digit   [#permalink] 07 Aug 2018, 16:49
Display posts from previous: Sort by