Problem 117. Distance walked 3D

Brilliant!

Can you explain the problem. Walking from [3 4 2] to [0 0 2] gives (3-0)+(4-0) = 7 units. Then from [0 0 2] to [0 1 2] gives 1 unit. From [0 1 2] to [1 1 2] gives 1 unit and finally from [1 1 2] to [1 1 20] gives 18 units. So sum of distance is 7+1+1+18 = 27. Is it right?

Walking from [3 4 2] to [0 0 2] is the same as walking DIRECT (along a 'diagonal') from the FIRST point that is 3 metres East, 4 metres North and 2 metres Elevated from the Origin to a SECOND point that is 0 metres East, 0 metres North and 2 metres Elevated from the Origin. As the Elevation hasn't changed in this leg of the trip, the distance reduces to the length of the hypotenuse of a right-angled triangle whose other sides are 3m and 4m, namely a length of 5 metres.