How many 6x9 pavers needed to cover 90 square feet?

Answer 1

In theory the answer is 240 tiles but this assumes that the area is "well behaved" and, if not, that you are prepared to use all the offcuts to fill bits in mosaic-style. A shape which in 17 inches wide, for example, will require a lot more pavers.

Answer 2

A paver will cover 54 square inches. You will have 12,960 square inches to cover. So you will need 240 pavers plus some for breakage.