If 1 trillion one dollar bills were placed flat in a rectangle with no gaps and no overlap, how many square meters would the dollar bills cover

One dollar bills size is 2.61 squared inches

and 1 squared inch equals 0.00064516 meter

one trillion is: 1,000,000,000,000,000,000

So the size of the dollar bill in meters is:

(2.61) (0.00064516) = 0.0016 squared meters

therefore the area covered by the dollar bills is:

1,000,000,000,000,000,000 * 0.0016

= 1.6 x 10^15 square meters

that is scientific notation (1.6 followed by 15 zeroes)