projectiles questionn

You're looking for values of t for which vertical displacement is 5m (since it starts 1m above the ground). The setup implies that it just passes the wall when it's coming down, so take the greater value of t. Once you find that, use the horizontal velocity component to calculate distance with distance = velocity * time

Thanks but for the vertical displacement bit in the question it says "She throws a stone as before and it just passes over the wall" Why are we assuming that the highest vertical displacement reached is when the stone just passes over the wall?