Question 315130: a two digit number is such that the product of its digit it equal to 20.if 9 is added to the number the digits interchange their places.find the number
Answer by malaydassharma(59)   (Show Source):
You can put this solution on YOUR website! let x= once digit and y is tenth digit.
Then , number is 10y+x
So, if the digits interchange their places, then the number is 10x+y
now,
xy=20 ....(i)
10y+x+9=10x+y
or 9x-9y=9
or x-y=1 ..(ii)
From (i) and (ii) , we get
x(x-1)=20=4X5
x=4 or 5 , but as x-y=1 , then x=5 and y=4
The number is 45.
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