A number consist of two digits the sum of the digit is 9.if 63 is subtracted from the number , it's digits are interchange. find the number
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A number consists of two digits. The sum of the digits is 9. If 63 is subtracted from the number, its digits are interchanged. What is the number?
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Slim Chackroun, .Net Software Engineer at EDF (2017-present)
Answered Aug 23, 2017
Off the top of my head, my first reflection was to notice that the number had only its digits interchanged which means it still had the same sign; And you stated it only consists of 2 digits; Thus leading me to assume that it is a positive number.
Therefore, It’s a 2 digits number that is bigger than 63 and less than or equal to 99.
Out of the box, there are only 3 numbers that fulfill all of this : 72, 81 and 90.
72 - 63 = 9
81 - 63 = 18 ( Bingo ! )
You probably wonder why the hell doesn’t this dude give us a well-tailored answer with the traditional X and Y variables and resort to finding the logical 2 equations that would undoubtedly solve this problem with style, which would also be applied to similar problems in the future, as any good mathematician would do.
I come from a competitive programming background where you train your mind to find patterns, shortcuts or clues and get used to solve a specific problem in a ridiculously short amount of time and rely on your logic to move on whenever you find the answer.
I thought I should share it, it might be interesting to some.
Still have a question? Ask your own!
What is your question?
Promoted by UpGrad.com
Post graduate diploma in data science from IIIT Bangalore.
Build your science career, choose your specialization, 3 month capstone project.
Apply Now
100+ ANSWERS

Slim Chackroun, .Net Software Engineer at EDF (2017-present)
Answered Aug 23, 2017
Off the top of my head, my first reflection was to notice that the number had only its digits interchanged which means it still had the same sign; And you stated it only consists of 2 digits; Thus leading me to assume that it is a positive number.
Therefore, It’s a 2 digits number that is bigger than 63 and less than or equal to 99.
Out of the box, there are only 3 numbers that fulfill all of this : 72, 81 and 90.
72 - 63 = 9
81 - 63 = 18 ( Bingo ! )
You probably wonder why the hell doesn’t this dude give us a well-tailored answer with the traditional X and Y variables and resort to finding the logical 2 equations that would undoubtedly solve this problem with style, which would also be applied to similar problems in the future, as any good mathematician would do.
I come from a competitive programming background where you train your mind to find patterns, shortcuts or clues and get used to solve a specific problem in a ridiculously short amount of time and rely on your logic to move on whenever you find the answer.
I thought I should share it, it might be interesting to some.
rudra86:
now don't give any feedback and don't give any answer s
Answered by
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Answer:
Step-by-step explanation:
Given :-
A number consist of two digits the sum of the digit is 9.
If 63 is subtracted from the number, it's digits are interchange.
To Find :-
The Number
Solution :-
Let the ten's digit be x.
And the unit's digit be (9 - x).
According to the question
Number = 10x + (9 - x) = 9x + 9.
Number obtained by reversing the digits
⇒ 10 (9 - x) + x = 90 - 9x.
⇒ (9x + 9) - 63 = 90 - 9x
⇒ 18x = 144
⇒ x = 144/18
⇒ x = 8.
Ten's digit = 8
Unit's digit = 1.
Hence, the required number is 81.
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