Two girls, standing at opposite ends of a rope, each makes a pulse of the same speed, Pulse A, with an amplitude of 4 cm, moves to the left and pulse B, with an amplitude of -6 cm, moves to the left. The pulses meet at point C.

When the two pulses meet at point C, Pulse A (amplitude $4 \text{ cm}$) and Pulse B (amplitude $-6 \text{ cm}$) overlap. The resultant pulse will have an amplitude of $4 \text{ cm} + (-6 \text{ cm}) = -2 \text{ cm}$. This means the resultant pulse will be a downward pulse with an amplitude of $2 \text{ cm}$.

      A (4 cm)
      / \
     /   \
----C-----
     \   /
      \ /
      B (-6 cm)

At point C, the rope will momentarily be displaced downwards by $2 \text{ cm}$.
The diagram should show pulse A moving right, pulse B moving left, and at point C, a smaller downward pulse representing the sum of the two.