Given:
Length of the rectangular poster = 2.5 feet.
Width of the rectangular poster = 3.5 feet
To find the length of the tape used around the edge of the poster, we simply need to calculate the perimeter of the rectangular poster.
That is;
Perimeter of a rectangle = 2l + 2w
Perimeter of the rectangular poster = 2(2.5) + 2( 3.5)
=5 + 7
=12
Therefore, the length of the tape that he used around the edge of the poster is 12 feet.
