1.

A two digit number is such that the product of digit is 8 . when 18 is added to the number , the digits are reversed . The number is:

Answer» Let the digits of the number are `x` and `y` where `y` is the unit digit.
Then, the number will be `10x+y`.
It is given that,
` xy = 8=>x = 8/y->(1)`
Also,
`10x+y +18 = 10y+x`
`=>9x-9y = -18`
`=>x-y = -2`
`=>8/y - y = -2`
`=>8-y^2 = -2y`
`=>y^2-2y -8 = 0`
`=>y^2-4y+2y -8 = 0`
`=>y(y-4)+2(y-4) = 0`
`=>(y+2)(y-4) = 0`
`=> y = -2 or y = 4`
We will take positive value for `y`, that is `4`.
`:. x = 8/y = 8/4 = 2`
So, the number is `2**10+4 = 24.`


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