In purely mathematical terms,
the area of a 16"x16" paver is 16*16 sq in = 1.33...*1.33... = 1.77... sq ft
So, to cover 400 sq feet you would need 400/1.77... = 225 pavers.
But this assumes that all the offfcuts are used - a very unrealistic assumption in real life. It also assumes that there is no wastage - another unrealistic assumption.
So, if the question is simply mathematical, the answer is 225 pavers but in real life you would be better off going for 10% more - say 245.
78.47 Pavers
You would need 20 pavers 20 times which is 20x20=400.
144 Get 160 to be safe.
72 Get 80 to be safe.
297 16x16-inch tiles.
It depends on the units used to measure the pavers: inches, centimetres, cubits, etc. It is not possible to answer the question without that information.
78.47 Pavers
You would need 20 pavers 20 times which is 20x20=400.
111 if you can cut 10 exactly in half to make 20 half pavers
144 Get 160 to be safe.
72 Get 80 to be safe.
297 16x16-inch tiles.
16 inch x 16 inch = 16x16/144 = 1.777777.... sq.ft. 450/1.777777..... = 253.125 tiles (not counting any wastage caused by cutting, breakage, etc) = 254 tiles minimum.
16x16 square feet = 256 square feet, so two tiles will suffice.
144.63 pavers
The answer depends on the measurement units used for 16x16. The answer also depends on the shape of the 390 sq ft area to be covered because the more irregular the shape, the greater the number of pavers you will need to cut. That is likely to result in some breakage. Furthermore, you may not want to use all the offcuts since that will make part of the area into a mosaic.
4.5 pavers will cover 1 sq foot. So 4.5 x 360 =1620 pavers