Mashrur's palindromes

Algebra Level 2

A palindrome is a number that remains the same when its digits are reversed. The numbers x x and x + 32 x+32 are three-digit and four-digit palindromes, respectively. What is the value of x x ?

This problem is shared by Mashrur F .


The answer is 969.

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10 solutions

The first 4 digit palindrome is 1001 with the next being 1111. We find that we only get a three digit number when we subtract 32 from 1001.Therefore this is the only number.

Moderator note:

Great approach which limits the number of cases that we have to check. Most solutions work from x x , and try to determine x + 32 x + 32 . In this solution, we determine that the only possible value for x + 32 x+32 is 1001, and hence the answer is determined.

This restriction will work for values up to 110, when the next 4-digit palindrome comes into play. The main idea here is that the 4-digit palindromes are rarely (going from 1000), than compared to the 3-digit palindromes.

Sourav Chaudhuri
Aug 12, 2013

Since the numbers differ by 32 and one is a 3 digit number and the other is a 4 digit number, the 4 digit number starts and ends with 1, and the 3 digit number starts and ends with 9. The numbers being abba and xyx Their values being 1000a+100b+10b+a and 100x+10y+x and the values of a and x being 1 and 9 respectively. The equation now becomes 1001+110b= 909+10y+32 simplifying the equation we get 1001-941=10y-110b or 60=10y-110b Now for all non zero values of b the equation takes negative values. The only non negative values which satisfy the equation are b=0 and y=6 Thus 1001 and 969

Moderator note:

Good explanation for why only 1 solution exists.

Prakirti Prakhar
Aug 13, 2013

x can at most be 999, so x+32 is at most 1031. Another constraint is that the minimum value x+32 can have is 1000. But the only palindrome between 1000 and 1031 is 1001, which means that x+32 is 1001. Hence, x=969.

969(three-digit palidrome) + 32 = 1001(four digit palidrome)

three-digit palidrome must be above 968 then only when you 32(a two-digit number) to it,it will become a four digit palidrome.

ramsandesh ramachandruni - 7 years, 10 months ago
Kalyph Dioquino
Aug 17, 2013

LOL i just guess

Josh Petrin
Aug 16, 2013

Since only 32 32 is being added to x x to produce a 4-digit number, we notice that x x must have hundreds digit 9 9 , and, since x x is a palindrome, its units digit must be 9 9 as well. Also, we notice that x + 32 x + 32 must have thousands digit of 1 1 , and therefore, units digit of 1 1 . And, since x x must have hundreds digit of 0 0 , x + 32 = 1001 x + 32 = 1001 , and x = 969 x = \boxed{969} .

Leah Williams
Aug 16, 2013

You have a four-digit palindromes, so you would do 1001-32= 969 969 would be your answer

Björn Nilsson
Aug 13, 2013

A three digit palindrome that turns larger than 1000 when adding 32 can only be: 969, 979, 989 and 999. Test adding 32 to those four!

as we must find the palindrome that is 900 or up and if we add up 32 at least we obtain a palindrome that is 4 digit , the closest is 1001 thus we know the 4 digit palindrome , or x+32 is 1001 so we can subtract 32 from 1001 to obtain the x here is the following details 1001-32 = 969 and it's fulfilled because 969 is palindrome indeed

Soumyarup Lahiri
Aug 11, 2013

Since x is a three digit number and by adding 32 to x, a four digit number is obtained, thus x must be greater than 968. The nest Palindrome number after 968 is 969. 969+32=1001 which is also a palindrome thus x = 969

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