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A palindrome is a number that reads the same forward and backward.

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A palindrome is a number that reads the same forward and backward.  [#permalink]

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New post Updated on: 21 Jul 2018, 04:53
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Question Stats:

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Permutation and Combination - Practice Question #2

2-A palindrome is a number that reads the same forward and backward. For example, 1221 and 232 are palindromes. By using the numbers from 0-9, how many 5-digit palindromes can be created.

Options

    a) 648
    b) 729
    c) 800
    d) 900
    e) 1000

To solve Question 1: Question 1

To solve Question 3: Question 3

To read our article: Must Read Articles and Practice Questions to score Q51 !!!!

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Originally posted by EgmatQuantExpert on 20 Jul 2018, 05:24.
Last edited by chetan2u on 21 Jul 2018, 04:53, edited 3 times in total.
Shifted the topic from DS to PS
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A palindrome is a number that reads the same forward and backward.  [#permalink]

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New post Updated on: 16 Dec 2018, 11:04

Solution



Given:
    • A palindrome is a number that reads the same forward and backward.

To find:
    • By using the numbers from 1-9, how many 5-digit palindromes can be created

Approach and Working:

Let the 5-digit number is abcba.

So, we need to find the in how many we can fill a, b, and c since the last two digits will take the same number.
    • a can take 9 numbers from 1-9.
    • b can take 10 numbers from 0-9.
    • c can take 10 numbers from 0-9.

Thus, way to form a 5-digit palindrome number= 9 * 10 * 10 *1 *1= 900.

Hence, the correct answer is option D.

Answer: D
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Originally posted by EgmatQuantExpert on 20 Jul 2018, 05:27.
Last edited by EgmatQuantExpert on 16 Dec 2018, 11:04, edited 6 times in total.
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Re: A palindrome is a number that reads the same forward and backward.  [#permalink]

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New post Updated on: 20 Jul 2018, 07:30
EgmatQuantExpert wrote:
Permutation and Combination - Practice Question #2

2-A palindrome is a number that reads the same forward and backward. For example, 1221 and 232 are palindromes. By using the numbers from 0-9, how many 5-digit palindromes can be created.

Options

    a) 648
    b) 729
    c) 800
    d) 900
    e) 1000

To read our article: Must Read Articles and Practice Questions to score Q51 !!!!


I am getting 5 arrangements

ABCBA- Total arrangement A(10)*B(9)*C(8)=720 , A can be selected in 10,b in 9 and C in 8 ways
ABBBA- Total arrangement A(10)*B(9)=90
ABABA-Total arrangement A(10)*B(9)=90
AAAAA- Total arrangement A(10)=10
ABBBA-Total arrangement A(10)*B(9)=90


Total=720 +90+90+90+10=1000
Considering 0 also since its not telling 5 digit number . correct me if i am wrong

Originally posted by kunalcvrce on 20 Jul 2018, 06:28.
Last edited by kunalcvrce on 20 Jul 2018, 07:30, edited 1 time in total.
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Re: A palindrome is a number that reads the same forward and backward.  [#permalink]

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New post 20 Jul 2018, 06:57
900?

- - - - - 5 places to filled. 1 blank can be filled in 9 ways.(1-9) last blank in 1 way as it has to be the same number as the 1 blanck. 2 blank can be filled in 10 ways (0-9). similarly 4 blank can be filled in 1 way only. lastly the 3 blank can also be filled in 10 ways
so 9*10*10=900
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Re: A palindrome is a number that reads the same forward and backward.  [#permalink]

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New post 20 Jul 2018, 23:03
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Re: A palindrome is a number that reads the same forward and backward.  [#permalink]

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New post 21 Jul 2018, 04:06
EgmatQuantExpert wrote:
Permutation and Combination - Practice Question #2

2-A palindrome is a number that reads the same forward and backward. For example, 1221 and 232 are palindromes. By using the numbers from 0-9, how many 5-digit palindromes can be created.

Options

    a) 648
    b) 729
    c) 800
    d) 900
    e) 1000

To solve Question 1: Question 1

To solve Question 3: Question 3

To read our article: Must Read Articles and Practice Questions to score Q51 !!!!


Number is of the form abcde
a can be filled in 9 ways (1-9)
b can be filled in 10 ways (0-9)
c can be filled in 10 ways (0-9)
d=b, so 1 way
e=a, so 1 way
total = 9*10*10*1*1 = 900
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Re: A palindrome is a number that reads the same forward and backward.  [#permalink]

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New post 23 Jul 2018, 05:57
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A palindrome is a number that reads the same forward and backward.  [#permalink]

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New post 15 Dec 2018, 11:12
EgmatQuantExpert wrote:

Solution



Given:
    • A palindrome is a number that reads the same forward and backward.

To find:
    • By using the numbers from 1-9, how many 5-digit palindromes can be created

Approach and Working:

Let the 5-digit number is abcba.

So, we need to find the in how many we can fill a, b, and c since the last two digits will take the same number.
    • a can take 9 numbers from 1-9.
    • b can take 10 numbers from 0-9.
    • c can take 10 numbers from 0-9.

Thus, way to form a 5-digit palindrome number= 9 * 10 * 10 *1 *1= 729.

Hence, the correct answer is option D.

Answer: D

EgmatQuantExpert , a couple of items are inconsistent.

It appears that Question #2:
1) ought to list 0-9 as the digits that are available in both topic threads (the solution prompt needs to be edited to match original);
2) ought to have a calculation error corrected.

Issues
(1) 0-9 or 1-9?
In the original prompt for Q #2, the available digits are integers 0-9. In the solution prompt (please see highlights above), both (1-9) and (0-9) are listed.

The original prompt for Question #2 that lists 0-9 is HERE
Quote:
By using the numbers from 0-9, how many 5-digit palindromes can be created.

(2) the second post on Q#2 solution has a calculation error, although the OA is listed correctly.
Quote:
Thus, way to form a 5-digit palindrome number= 9 * 10 * 10 *1 *1= 729.

(9 * 10 * 10 * 1 * 1) = 900, not 729.

It appears that Questions #1 and #2 got mixed up. The answer to Question 1 HERE, (answer is HERE) is 729.
In Question #1, the digits are limited to 1-9.

I think Q#2
-- needs to state that integers are 0-9 in all posts and
-- needs to have the written answer changed to 900

Would you please correct the inconsistencies?
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Re: A palindrome is a number that reads the same forward and backward.  [#permalink]

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New post 16 Dec 2018, 01:10
EgmatQuantExpert :

quoting your line
Thus, way to form a 5-digit palindrome number= 9 * 10 * 10 *1 *1= 729.

it should be 900 not 729..


EgmatQuantExpert wrote:

Solution



Given:
    • A palindrome is a number that reads the same forward and backward.

To find:
    • By using the numbers from 1-9, how many 5-digit palindromes can be created

Approach and Working:

Let the 5-digit number is abcba.

So, we need to find the in how many we can fill a, b, and c since the last two digits will take the same number.
    • a can take 9 numbers from 1-9.
    • b can take 10 numbers from 0-9.
    • c can take 10 numbers from 0-9.

Thus, way to form a 5-digit palindrome number= 9 * 10 * 10 *1 *1= 729.

Hence, the correct answer is option D.

Answer: D

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Re: A palindrome is a number that reads the same forward and backward.  [#permalink]

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New post 16 Dec 2018, 11:05
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Re: A palindrome is a number that reads the same forward and backward.   [#permalink] 16 Dec 2018, 11:05
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