On a morning walk, three persons step off together and their steps measure 40 cm, 42 cm, and 45 cm respectively. What is the minimum distance each should walk so that each can cover the same distance in complete steps?

To find the minimum distance each person should walk so that they can cover the same distance in complete steps, we need to find the least common multiple (LCM) of their step lengths.

The given step lengths are 40 cm, 42 cm, and 45 cm. To find the LCM, we can list the multiples of each number and look for the smallest common multiple.

Multiples of 40: 40, 80, 120, 160, 200, 240, 280, 320, 360, 400, ...
Multiples of 42: 42, 84, 126, 168, 210, 252, 294, 336, 378, 420, ...
Multiples of 45: 45, 90, 135, 180, 225, 270, 315, 360, 405, 450, ...

By examining the multiples, we can see that the least common multiple of 40, 42, and 45 is 1,260.

Therefore, each person should walk a minimum distance of 1,260 cm (or 12.6 meters) so that they can cover the same distance in complete steps.