Let the 5 digit number be represented by abcde.

Then the 6 digit number, 1abcde x 3 = abcde1 (another 6 digit number)

Now let Y = abcde.00

Then (100000 + Y) x 3 = (Y x 10) + 1

300000 + 3Y = 10Y + 1

7Y = 299999

Y = 299999 รท 7 = 42857

Check : 3 x 142857 = 428571

Then the 6 digit number, 1abcde x 3 = abcde1 (another 6 digit number)

Now let Y = abcde.00

Then (100000 + Y) x 3 = (Y x 10) + 1

300000 + 3Y = 10Y + 1

7Y = 299999

Y = 299999 รท 7 = 42857

Check : 3 x 142857 = 428571