Answer:
22.44 meters
Explanation:
Solution: 
First find LCM(51,68)=204. 
 
So their footsteps coincide every time after Nick's 204÷51 = 4th step and his dad's 204÷68 = 3rd step. 
 
So, in the distance of 204 cm, there will be total 6 footsteps, except in the first 204 cm when their "starting" step is counted. 
 
The total distance will be 67 − 1 (starting step)/6 · 204 = 2244 cm or 22.44m.