A certain positive integer N is twice the product of its digits.

Find N.

10x + y = 2xy
so te number is even.. implied y is element of {2,4,6,8}.
solving the above equation,
y=2, 10x + 2 = 4x => x = -1/3 ( not valid )
y=4, 10x + 4 = 8x => x = -2 ( not valid )
y=6, 10x + 6 = 12x => x = 3
y=8, 10x + 8 = 16x => x = 4/3 ( not valid )

so x =3, y =6.. answer = 36

Posted by shiva on 2020-04-30 01:35:24