Three children are on the floor playing with building blocks.
Three kids play with building blocks on the carpet.
The children do not have to be on the carpet to be on the floor.  The floor may not be carpeted.
exists p1 x1 x2 x3.(n_playing(x2) & of(x2,x3) & n_floor(x3) & exists x4 x5.(on(x1,x2) & with(x2,x4) & n_block(x4) & of(x4,x5) & n_building(x5)) & n_child(x1) & card_eq_3(x1))
exists e1 x1 x2 x3 x4.(n_carpet(x4) & on(e1,x4) & with(e1,x2) & n_block(x2) & of(x2,x3) & n_building(x3) & Actor(e1,x1) & v_play(e1) & n_kid(x1) & card_eq_3(x1))