Expressed as a ratio, the board lengths are 1:3.
Then the sum of the "ratio units" is 1+3=4, so each "ratio unit" must represent (48 in)/4 = 12 in of board.
The piece that is 1 ratio unit long is 1*12 in = 12 in.
The piece that is 3 ratio units long is 3*12 in = 36 in.
The pieces are 12 in and 36 in long.
