A palindrome is a number that reads the same forward and

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

30 Mar 2012, 05:00

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63% (01:20) correct

36% (00:45) wrong

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A palindrome is a number that reads the same forward and backward, such as 121. How many odd, 4-digit numbers are palindromes?

A. 40
B. 45
C. 50
D. 90
E. 2500

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Re: Palindrome [#permalink]

30 Mar 2012, 05:05

pratikbais wrote:

A palindrome is a number that reads the same forward and backward, such as 121. How many odd, 4-digit numbers are palindromes?

a) 40

b) 45

c) 50

d) 90

e) 2500

We want to determine how many odd 4-digit numbers like XYYX are there. Notice here that in a palindrome X and Y can be the same, for example 1111 or 3333 are also palindromes.

Since, the number must be odd then the first and the last digits (X's) can take 5 values (1, 3, 5, 7, or 9) and the two middle digits (Y's) can take 10 values (0, 1, ..., 9), so total such numbers possible is 5*10=50.

Answer: C.

Hope it's clear.
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Re: Palindrome [#permalink] 30 Mar 2012, 05:05

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A palindrome is a number that reads the same forward and

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A palindrome is a number that reads the same forward and

A palindrome is a number that reads the same forward and

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