Six colleagues — G, H, I, J, K and L — sit in a row of six chairs, all facing north, with the chairs numbered from left to right. J sits second to the right of G. I sits at one of the two extreme ends. H sits third to the left of L. K sits immediately to the right of H. Neither K nor J sits at an extreme end. How many persons sit between K and I?

Try I at the right end (chair 6): H and L are three apart and K is right next to H, so H = 1, K = 2, L = 4; then G and J (J two places right of G) must fill chairs 3 and 5 → G = 3, J = 5. Order: H, K, G, L, J, I. With I at the left end instead, J would land on chair 6, an extreme end, which is not allowed. K is on chair 2 and I on chair 6, so G, L and J — three persons — sit between them.