Here's my thought -
From one 42" strip you should cut 9 - 4 1/2" pieces.
You need 2 strips (18) pieces per one block (12" finished)
For a twin size you need 5 x 7 blocks (35).
Two strips per block comes to 70 strips,
That's 2 bundles of 40 strips, and the leftovers can be used for the border