Question

the sum of the digits of a two digit no. is 7.If two is subtracted from the no. formed by interchanging the digits,the result isdouble the original no. .Find the original no.​

Answer 1

Let the original number be  

yx

​  

; i.e., 10y+x. We know x+y=7.  The number obtained by reversing the digits in  

xy

​  

, i.e., 10x+y. The second condition gives 10x+y−2=2(10y+x). Thus we have two equations:

x+y=7....(1)

8x−19y=2....(2)

Multiply the equation (1) by 19 and get

19x+19y=133.

Adding this to (2), we obtain 27x=135. This gives x=5. Hence y=7−x=7−5=2.

The required number is 25.

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Answer 2

Answer:

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