At Meribah, how many times did Moses strike the rock with his staff?

Answer: Twice

God told Moses to speak to the rock, but he struck it twice with his staff, and a great amount of water gushed out.

“Then Moses raised his hand and struck the rock twice with his staff, so that a great amount of water gushed out, and the congregation and their livestock were able to drink.”— Numbers 20:11 (BSB)