Answer
The board is now 1.26m long.
Work Step by Step
Convert the length of the board that was removed to m.
$78cm\times\frac{1m}{100cm}=0.78m$
Move the decimal to convert 4cm to 0,04m.
2m 4cm is 2.04m.
Subtract the length that was cut off from the original length of the board to find the current length.
$2.04m-0.78m=1.26m$