A logic problem by Mohammad Khaza

From green bar, it's clear that the height of vertical bar = 2/3 of uninterrupted shadow length

Therefore shadow of 6m of red bar indicates the height of 4m. The remaining red bar casts a direct 1:1 vertical projection on the wall.

Therefore total length = 4m + 4m = 8m.

The 4-metre shadow on the wall, when cast on the ground, will be $\dfrac{3}{2}\times 4=3\times 2=6$ metres by proportion. So if the entire shadow of the red bar were cast on the ground, it would be $6+6=12$ metres in length, which means its actual height is $\dfrac{2}{3}\times 12=2\times 4=\boxed{8}$ metres.