Johnny your friend claims that the green trail is 10 miles longer than the pink Trail. what calculation error might Johnny have made ? what is correct comparison of the length of the pink trail to the length of the green trail ?

First, measure the length of each trail:
Green trail: 2+2+1+1.5+0.5+1.5+0.5+1+0.5+0.5 = 11 miles
Pink trail: 3.5+1+1+0.5 =5
Subtract the lengths to find the difference:
11-5 = 6
The green trail is 6 miles longer than the pink trail.
The calculation error of Jhony was counting each unit as a whole mile instead of 1/2 a mile (0.5)