The Quran does not say that Egypt suffered only nine plagues, nor does it claim to reproduce the Exodus account scene by scene. The phrase "nine signs" refers to a set of signs given to Moses, and the Quran's silence about Passover is an omission of detail, not a contradiction.
What the objection fairly points out
Exodus presents a sequence of ten plagues, ending with the death of the firstborn, after which Pharaoh allows Israel to leave. It then establishes Passover as a lasting memorial. The Quran mentions several afflictions - including the flood, locusts, lice, frogs, and blood - but does not mention Passover, the death of the firstborn, or the plague of darkness. A critic may therefore ask why a revelation claiming to recount Moses' history would leave out what Exodus treats as central.
What "nine signs" actually means
The key point is that the Quran does not call the nine signs "nine plagues." It says:
"And We certainly gave Moses nine clear signs. So ask the Children of Israel when he came to them and Pharaoh said to him, 'Indeed I think you, O Moses, are affected by magic.'"
Quran 17:101
It also says:
"And put your hand into the opening of your garment; it will come out white without disease - among nine signs to Pharaoh and his people. Indeed, they have been a people defiantly disobedient."
Quran 27:12
In both passages, the subject is signs given to Moses in his confrontation with Pharaoh, not a numbered list of every punishment sent upon Egypt. Classical commentators, including al-Tabari and Ibn Kathir, transmitted differing explanations of the nine. These commonly include the staff, the radiant hand, and the afflictions listed in Quran 7:133, with variations over how drought and crop loss are counted. That interpretive discussion itself shows why equating "nine signs" with the ten plagues is too quick.
Why Passover is not mentioned
The Quran repeatedly retells prophetic history selectively. Its purpose is guidance, warning, and correction, not a complete chronological transcript of earlier scriptures. It can mention Pharaoh's tyranny, Moses' signs, the exodus, and the drowning of Pharaoh while leaving out other episodes. Omission does not imply denial.
Passover also carries a specifically Israelite covenantal role in Exodus, while Christian interpretation gives it a further typological meaning concerning Jesus. The Quran does not adopt that later theological framework, but it is not required to mention every institution or symbol in order to affirm that Moses was a real prophet and that Pharaoh was judged.
Thus, the passage establishes neither that the Quran confused ten plagues with nine nor that it invented a half-remembered story. It does show that the Quran presents the episode with a different selection and purpose. Whether one accepts the Quran's revelation is a larger question, but this particular argument depends on treating "nine signs" as "nine plagues," which the text itself does not say.