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Answers
let the ones digit place be x then the tens digit place will be 10 (9-x)
new digit 10×x +9-x
we have,
10x+9-x - 10(9-x)+x=27
9x+9-90+9x=27
18x=27+90-9
18x=108
x=108/18=6
the two digits are 36.
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Answer :
36
Solution :
Let the tens digit and the unit digit of the required two digits number be x and y respectively .
Then ,
Required (Original) number = 10x + y
Also , it is given that the sum of digits of the required number is 9 .
ie. x + y = 9 --------(1)
Now ,
On interchanging the digits of the original number , the tens digit and the unit digit of the new number will be y and x respectively .
Then ,
New number = 10y + x
Now ,
According to the question , on interchanging the digits of original number , the resulting number is greater than original number by 27 .
Thus ,
=> 10y + x = 10x + y + 27
=> 10y + x - 10x - y = 27
=> 9y - 9x = 27
=> 9(y - x) = 27
=> y - x = 27/9
=> y - x = 3 --------(2)
Now ,
Adding eq-(1) and (2) , we get ;
=> x + y + y - x = 9 + 3
=> 2y = 12
=> y = 12/2
=> y = 6
Now ,
Using eq-(1) , we have ;
=> x + y = 9
=> x + 6 = 9
=> x = 9 - 6
=> x = 3
Hence,
The required number is 36 .
Alternative :
By inspection (not to be used in subjective exams) -
Here it is given that , the sum digits of a two digits number is 9 .
And on interchanging the digits of original number , the resulting number is greater than original number by 27 .
(ie. new number > original number)
Now ,
Let's write all the possible two digits numbers whose sum of digits is 9 and whose interchanged number is greater than the original number .
Original no. New no. after
interchanging the digits
18 81
27 72
36 63
45 54
Clearly ,
For the number 36 , the new number obtained on interchanging the digits is 63 which is greater than 36 by 27 .
Hence ,
Required number is 36 .